You migrate by building the new phone system next to the old one, then moving your phone numbers across on a date the old carrier has confirmed. The number move is called a port. Its date depends on the carrier you're leaving, and undoing it means porting again, so the plan is arranged around it. Take inventory first, build and try the new system before the port, test inbound calls right after it, and cancel the old service last.
\n","summary":"Build the new phone system beside the old one, then port your numbers on a date the old carrier has confirmed. Inventory numbers, call flows and analog devices first, decide what moves to the cloud and what stays, pilot on temporary numbers, test inbound calls right after the port, and cancel the old service last.","publishedAt":"2026-05-05T19:57:25.984","verifiedAt":"2026-09-14T00:00:00","editorialStatus":"APPROVED","lastReviewedAt":"2026-10-10T04:04:18.366","nextReviewDueAt":"2026-12-14T00:00:00","templateVersion":"v2","aliases":["PBX to UCaaS migration steps","How do you move from an on-premises phone system to the cloud?","On-prem PBX to cloud phone migration plan","What order do you migrate a PBX to UCaaS in?","How do you port numbers from a PBX to a cloud phone system?","Legacy PBX to cloud phone system cutover plan"],"confidenceScore":76,"confidenceLabel":"Medium","canonicalUrl":"https://sangoma.com/blog/how-to-switch-from-on-premises-pbx"},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"contributorOrganizationProfile":null,"contributorPerson":null,"sections":[{"id":"8a800047-0484-4234-8290-304c0bba640c","sectionKey":"inventory","sectionType":"markdown_section","heading":"Start with what the PBX and its lines do today","introMarkdown":"A port moves phone numbers. It doesn't move the settings inside the PBX, the routing behind the main number, or the devices plugged into the wall. Whatever callers to a number relied on has to be rebuilt on the new system or deliberately kept on the old one. That is why the inventory has three parts.\n\nThe first is the numbers themselves, with the account each one sits on. Microsoft's [guide to planning a port](https://learn.microsoft.com/en-us/microsoftteams/phone-number-calling-plans/port-order-overview), written for its own calling plans, lists what a port order asks for. It needs the account number, the person authorized on the account, the service address, the business name, the billing telephone number and the list of numbers. Most of that is on a recent invoice. In the United States you can also ask your carrier for the customer service record, which is its official record of the account. You can ask for it at any time.\n\nThe second is the call flows. Write down what happens when someone calls the main number during the day, after hours and on a holiday. Do the same for each department line and each group of phones that ring together.\n\nThe third is every device that uses a phone line and isn't a desk phone. Look for fax machines, alarm panels, elevator phones, paging systems and door intercoms. They matter because not every cloud phone system serves them, and [the copper lines some of them run on are being retired](https://www.answerstack.io/q/which-legacy-devices-are-still-at-risk-when-pstn-pots-lines-are-retired-or). Microsoft says a fax number can be ported to Teams, but faxing won't work there. It also warns that other services tied to a ported number, such as ISDN or broadband, are disconnected once the port completes.","introHtml":"A port moves phone numbers. It doesn't move the settings inside the PBX, the routing behind the main number, or the devices plugged into the wall. Whatever callers to a number relied on has to be rebuilt on the new system or deliberately kept on the old one. That is why the inventory has three parts.
\nThe first is the numbers themselves, with the account each one sits on. Microsoft's guide to planning a port, written for its own calling plans, lists what a port order asks for. It needs the account number, the person authorized on the account, the service address, the business name, the billing telephone number and the list of numbers. Most of that is on a recent invoice. In the United States you can also ask your carrier for the customer service record, which is its official record of the account. You can ask for it at any time.
\nThe second is the call flows. Write down what happens when someone calls the main number during the day, after hours and on a holiday. Do the same for each department line and each group of phones that ring together.
\nThe third is every device that uses a phone line and isn't a desk phone. Look for fax machines, alarm panels, elevator phones, paging systems and door intercoms. They matter because not every cloud phone system serves them, and the copper lines some of them run on are being retired. Microsoft says a fax number can be ported to Teams, but faxing won't work there. It also warns that other services tied to a ported number, such as ISDN or broadband, are disconnected once the port completes.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":10},{"id":"dc30a9d5-8e03-4673-87f6-1f6bf40debf7","sectionKey":"what_moves","sectionType":"markdown_section","heading":"Decide what moves to the cloud and what doesn't","introMarkdown":"A migration doesn't have to put everything in one place on one day. Atlantech Online's [business phone service](https://www.atlantech.net/solutions/voice/phone) shows the choices one provider can offer. You can connect to its cloud PBX. Or you can keep your own PBX and have service delivered to it by SIP, PRI or analog. For the analog devices, its [POTS replacement service](https://www.atlantech.net/solutions/voice/pots-replacement) puts a managed appliance in the telecom closet. The appliance gives fire panels, elevator phones, alarms and fax lines an analog line over broadband and 4G LTE. Each unit supports two to eight lines and has up to 24 hours of battery backup.\n\nSuppose a 60-person accounting firm has a PBX in a closet and 70 phone numbers. Sixty are direct lines, six are the main and department numbers, two are fax lines, one serves the fire alarm panel and one serves the elevator phone. The 60 staff and the six shared numbers move to the cloud phone system. The two fax lines, the fire panel line and the elevator line move to an analog appliance, four lines on one unit. That assumes each device works on the appliance and the fire panel's monitoring company tests its line after the move. The PBX is retired.\n\nA different firm might have a second site that isn't ready to change. It could keep that site's PBX for now and feed it with a SIP trunk, then move those users later.","introHtml":"A migration doesn't have to put everything in one place on one day. Atlantech Online's business phone service shows the choices one provider can offer. You can connect to its cloud PBX. Or you can keep your own PBX and have service delivered to it by SIP, PRI or analog. For the analog devices, its POTS replacement service puts a managed appliance in the telecom closet. The appliance gives fire panels, elevator phones, alarms and fax lines an analog line over broadband and 4G LTE. Each unit supports two to eight lines and has up to 24 hours of battery backup.
\nSuppose a 60-person accounting firm has a PBX in a closet and 70 phone numbers. Sixty are direct lines, six are the main and department numbers, two are fax lines, one serves the fire alarm panel and one serves the elevator phone. The 60 staff and the six shared numbers move to the cloud phone system. The two fax lines, the fire panel line and the elevator line move to an analog appliance, four lines on one unit. That assumes each device works on the appliance and the fire panel's monitoring company tests its line after the move. The PBX is retired.
\nA different firm might have a second site that isn't ready to change. It could keep that site's PBX for now and feed it with a SIP trunk, then move those users later.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":20},{"id":"34ce615f-5f60-46be-a6ff-3fca62a5fcc9","sectionKey":"destinations_table","sectionType":"table_section","heading":"Where each part of an old system can go","introMarkdown":null,"introHtml":null,"outroMarkdown":null,"outroHtml":null,"contentJson":{"rows":[{"cells":["Staff with desk phones on the PBX","Users on the cloud phone system, with apps or new handsets"]},{"cells":["A PBX you want to keep for now","Carrier service delivered to that PBX by SIP, PRI or analog"]},{"cells":["Fax, alarm, elevator and other analog lines","A managed analog appliance, or left with the current carrier"]}],"columns":["What you have today","Where it can go"]},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":30},{"id":"2d044859-9f18-49bc-b395-d11914ce3c65","sectionKey":"build_and_pilot","sectionType":"markdown_section","heading":"Build and try the new system before the port","introMarkdown":"Your published numbers keep ringing on the old PBX until the port happens. That gives you time to build the new system completely while nobody depends on it. Create the users, record the greetings and rebuild each call flow from the inventory. Enter an [emergency address for each location](https://www.answerstack.io/q/how-do-i-register-a-voip-phone-for-911). Staff who work from home need [a setup of their own](https://www.answerstack.io/q/how-do-you-set-up-ucaas-for-a-remote-team), because their 911 address and their network are at home.\n\nThen try it on temporary numbers. Ask the new provider for a few new numbers that aren't part of the port. Put one on the new main-number menu and the others on a small group of pilot users. Calling the temporary main number tests the menu, the queues and the after-hours path the way a caller will meet them. The pilot users make and take real calls at their desks, which shows how the new service behaves on the office network. A weak switch or a dead WiFi spot is easier to fix with five people on the system than with sixty.\n\nA pilot on temporary numbers has a limit. It tests whether the new system routes calls the way you intended. It can't show that the port will go through, because the published numbers haven't moved yet.","introHtml":"Your published numbers keep ringing on the old PBX until the port happens. That gives you time to build the new system completely while nobody depends on it. Create the users, record the greetings and rebuild each call flow from the inventory. Enter an emergency address for each location. Staff who work from home need a setup of their own, because their 911 address and their network are at home.
\nThen try it on temporary numbers. Ask the new provider for a few new numbers that aren't part of the port. Put one on the new main-number menu and the others on a small group of pilot users. Calling the temporary main number tests the menu, the queues and the after-hours path the way a caller will meet them. The pilot users make and take real calls at their desks, which shows how the new service behaves on the office network. A weak switch or a dead WiFi spot is easier to fix with five people on the system than with sixty.
\nA pilot on temporary numbers has a limit. It tests whether the new system routes calls the way you intended. It can't show that the port will go through, because the published numbers haven't moved yet.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":40},{"id":"3db05519-7276-4b97-b01a-dcde4d6b735c","sectionKey":"port_order_and_date","sectionType":"markdown_section","heading":"Order the port and plan around the confirmed date","introMarkdown":"The new provider submits the port order to your current carrier on your behalf. The current carrier then approves or rejects it. Microsoft's guide is plain about the date. Choosing a target date doesn't mean the port happens then. It happens on that date only if the current carrier approves it, and the approval is called a firm order commitment.\n\nMicrosoft's figures give a sense of the timing for a US port to its calling plans. The current carrier has three to five business days to respond. A port typically takes 7 to 14 days from start to finish and can take up to 30, depending on the carrier. A rejected order has to be corrected and resubmitted, and the response clock starts again. Microsoft names mismatched account details as the most common cause of errors and delays. A freeze on the account also blocks a port, and removing one can take one to three weeks.\n\nThose figures describe Microsoft's process, and another provider runs its own. Atlantech lists number porting in its [Operator Connect](https://www.atlantech.net/solutions/voice/operatorconnect) price. For its business phone service it advertises go-live \"in as few as 10-15 business days,\" on the condition that nothing is delayed on the client's end. A complete inventory removes one cause of delay on your side, since the details on the order have to match the carrier's records.\n\nSchedule the cutover for the confirmed date, and announce it to staff once you have that confirmation. An announced date that the carrier then rejects has to be announced twice.\n\nTwo rules about the old service follow from how ports work. Don't cancel or disconnect anything before the port completes, because inactive numbers can't be ported. And decide whether the port is full or partial. A full port moves every number on the account. A partial port leaves some behind, which is how a firm can keep an alarm line with its old carrier. If the billing telephone number is among the numbers leaving, Microsoft says one of the remaining numbers can become the new one.\n\nIf you port in stages from one account, the orders run one after another. Microsoft says the current carrier processes one order per account at a time and rejects any that overlap.","introHtml":"The new provider submits the port order to your current carrier on your behalf. The current carrier then approves or rejects it. Microsoft's guide is plain about the date. Choosing a target date doesn't mean the port happens then. It happens on that date only if the current carrier approves it, and the approval is called a firm order commitment.
\nMicrosoft's figures give a sense of the timing for a US port to its calling plans. The current carrier has three to five business days to respond. A port typically takes 7 to 14 days from start to finish and can take up to 30, depending on the carrier. A rejected order has to be corrected and resubmitted, and the response clock starts again. Microsoft names mismatched account details as the most common cause of errors and delays. A freeze on the account also blocks a port, and removing one can take one to three weeks.
\nThose figures describe Microsoft's process, and another provider runs its own. Atlantech lists number porting in its Operator Connect price. For its business phone service it advertises go-live "in as few as 10-15 business days," on the condition that nothing is delayed on the client's end. A complete inventory removes one cause of delay on your side, since the details on the order have to match the carrier's records.
\nSchedule the cutover for the confirmed date, and announce it to staff once you have that confirmation. An announced date that the carrier then rejects has to be announced twice.
\nTwo rules about the old service follow from how ports work. Don't cancel or disconnect anything before the port completes, because inactive numbers can't be ported. And decide whether the port is full or partial. A full port moves every number on the account. A partial port leaves some behind, which is how a firm can keep an alarm line with its old carrier. If the billing telephone number is among the numbers leaving, Microsoft says one of the remaining numbers can become the new one.
\nIf you port in stages from one account, the orders run one after another. Microsoft says the current carrier processes one order per account at a time and rejects any that overlap.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":50},{"id":"201a96f6-42b5-42bd-928e-7d6842e37337","sectionKey":"test_after_port","sectionType":"markdown_section","heading":"Test inbound calls as soon as the numbers move","introMarkdown":"On the confirmed date the old carrier releases the numbers, and the new provider starts receiving the calls. From then on a call to one of those numbers arrives at the new provider. In a migration that retires the PBX, like the firm's above, the PBX is no longer in the path.\n\nSo test from outside, with a mobile phone, and work through the inventory. Call the main number and follow each menu option. Call each department line and one or two direct lines. Leave a voicemail and confirm it arrives. Call again that evening to hear the after-hours path. Then call out from a desk and check the number the other person sees.\n\nFor 911, check the address on file without calling 911. Atlantech [documents dialing 933](https://care.atlantech.net/kb/articles/testing-e911) from a phone on its service. A recorded message reads back the phone number and the E911 address registered for it. That confirms the record. It doesn't test an emergency call itself.\n\nReturning a number to the old carrier is another port with another approval. So the first place to fix a problem after cutover is the new system. A menu that sends callers to the wrong place, or a queue that rings the wrong people, is a change to the new system's settings and needs no port. That is the reason to rebuild and try every call flow before the port.","introHtml":"On the confirmed date the old carrier releases the numbers, and the new provider starts receiving the calls. From then on a call to one of those numbers arrives at the new provider. In a migration that retires the PBX, like the firm's above, the PBX is no longer in the path.
\nSo test from outside, with a mobile phone, and work through the inventory. Call the main number and follow each menu option. Call each department line and one or two direct lines. Leave a voicemail and confirm it arrives. Call again that evening to hear the after-hours path. Then call out from a desk and check the number the other person sees.
\nFor 911, check the address on file without calling 911. Atlantech documents dialing 933 from a phone on its service. A recorded message reads back the phone number and the E911 address registered for it. That confirms the record. It doesn't test an emergency call itself.
\nReturning a number to the old carrier is another port with another approval. So the first place to fix a problem after cutover is the new system. A menu that sends callers to the wrong place, or a queue that rings the wrong people, is a change to the new system's settings and needs no port. That is the reason to rebuild and try every call flow before the port.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":60},{"id":"a714222c-ed56-4943-8282-6aed962576ab","sectionKey":"cancel_old_service_last","sectionType":"markdown_section","heading":"Cancel the old service last","introMarkdown":"Once every port is confirmed complete, close out the old service for the numbers and lines you moved. Keep active any line you deliberately left with the old carrier, such as an alarm or elevator line in a partial port. For a full port, Microsoft says the old account might be terminated automatically, and it still recommends working with the old provider to confirm the account is closed. Read the next invoice to see that billing has stopped for the lines you moved.\n\nBefore anyone unplugs the PBX, go back to the device list. A paging amplifier or a door intercom wired to the PBX can stop working when the PBX is switched off, whether or not it ever had a number to port. If the list shows nothing still attached, the PBX can go.","introHtml":"Once every port is confirmed complete, close out the old service for the numbers and lines you moved. Keep active any line you deliberately left with the old carrier, such as an alarm or elevator line in a partial port. For a full port, Microsoft says the old account might be terminated automatically, and it still recommends working with the old provider to confirm the account is closed. Read the next invoice to see that billing has stopped for the lines you moved.
\nBefore anyone unplugs the PBX, go back to the device list. A paging amplifier or a door intercom wired to the PBX can stop working when the PBX is switched off, whether or not it ever had a number to port. If the list shows nothing still attached, the PBX can go.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":70}],"citations":[{"title":"47 CFR 52.35, Porting intervals","url":"https://www.law.cornell.edu/cfr/text/47/52.35","excerpt":null,"quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-14T00:00:00","supportsText":"US rule: simple wireline-to-wireline and simple intermodal ports must complete within one business day unless a longer period is requested; non-simple ports within four business days; business days exclude the current service provider's company-defined holidays; intermodal ports include ports involv","domain":"law.cornell.edu","publisherName":"Legal Information Institute, Cornell Law School (reproducing the Code of Federal Regulations)"},{"title":"47 CFR 52.36 Standard data fields for simple port order processing","url":"https://www.law.cornell.edu/cfr/text/47/52.36","excerpt":null,"quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-14T00:00:00","supportsText":"US rule: the 14 data fields a carrier may require for a simple port order, including Agency Authority Status, with the passcode field optional unless assigned.","domain":"law.cornell.edu","publisherName":"Legal Information Institute, Cornell Law School"},{"title":"Local Number Portability Porting Interval and Validation Requirements, Report and Order (FCC 10-85)","url":"https://docs.fcc.gov/public/attachments/FCC-10-85A1.pdf","excerpt":null,"quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-14T00:00:00","supportsText":"Regulator order, adopted May 20, 2010: the four-part definition of a simple port (no unbundled network elements, single-line account only, no complex switch translations such as Centrex, ISDN, AIN services, remote call forwarding or multiple services on the loop, no reseller); the Agency Authority S","domain":"docs.fcc.gov","publisherName":"Federal Communications Commission"},{"title":"LNPA WG Best Practice 67: Processing Interval for Simple, Non-Simple, Porting Project and Customer Service Records","url":"https://docs.fcc.gov/public/attachments/DOC-309681A1.pdf","excerpt":null,"quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-14T00:00:00","supportsText":"Industry working group best practice: 4 hour firm order commitment for simple ports; 1 to 50 numbers on a request treated as non-simple with a 24 hour commitment and four business day interval; 51 or more treated as a project with commitment and due date negotiated between carriers and a project com","domain":"docs.fcc.gov","publisherName":"Local Number Portability Administration Working Group, published by the FCC"},{"title":"Microsoft - Port phone numbers overview","url":"https://learn.microsoft.com/en-us/microsoftteams/phone-number-calling-plans/port-order-overview","excerpt":null,"quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-09-14T00:00:00","supportsText":"Vendor documentation for Microsoft Calling Plans: the gaining provider becomes service provider of record and the old service can then be disconnected; billing telephone number, account number, account PIN, authorized user and service address requirements; full versus partial port and the replacemen","domain":"learn.microsoft.com","publisherName":"Microsoft"},{"title":"Transfer phone numbers to Microsoft Teams - Microsoft Teams","url":"https://learn.microsoft.com/en-us/microsoftteams/phone-number-calling-plans/transfer-phone-numbers-to-teams","excerpt":null,"quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-09-14T00:00:00","supportsText":"Vendor documentation: country-specific downloadable letter of authorization forms; e-signature or offline signature options; edits that affect the letter of authorization require a refreshed, re-signed letter before submission; account PIN distinct from a billing telephone number freeze PIN; partial","domain":"learn.microsoft.com","publisherName":"Microsoft Learn"},{"title":"Country/region availability - Audio Conferencing, Calling Plans - Microsoft Teams","url":"https://learn.microsoft.com/en-us/microsoftteams/calling-plan-overview","excerpt":null,"quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-09-14T00:00:00","supportsText":"Vendor documentation: availability does not indicate whether Know Your Customer verification is required; verify and obtain approval before acquiring or porting numbers; review is completed at tenant level and most reviews finish within three business days.","domain":"learn.microsoft.com","publisherName":"Microsoft Learn"},{"title":"Plan Direct Routing - Microsoft Teams","url":"https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan","excerpt":null,"quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-09-14T00:00:00","supportsText":"Vendor documentation: Direct Routing fits organizations requiring integration with third-party PBXs or analog devices; a single tenant can combine Calling Plan or Operator Connect for PSTN calling with Direct Routing for calls to third-party PBXs and for analog devices; infrastructure requirements o","domain":"learn.microsoft.com","publisherName":"Microsoft Learn"},{"title":"Set up an auto attendant","url":"https://learn.microsoft.com/en-us/microsoftteams/create-a-phone-system-auto-attendant","excerpt":null,"quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-09-14T00:00:00","supportsText":"Vendor documentation: auto attendant call routing options include redirecting a call to an external phone number, alongside a person in the organization, a voice app, a resource account, voicemail and announcements.","domain":"learn.microsoft.com","publisherName":"Microsoft Learn"},{"title":"Route calls to unassigned numbers","url":"https://learn.microsoft.com/en-us/microsoftteams/routing-calls-to-unassigned-numbers","excerpt":null,"quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-09-14T00:00:00","supportsText":"Vendor documentation: calls to unassigned numbers can be routed to a user, a resource account associated with an auto attendant or call queue, or an announcement; rules can be defined individually or as a range, with a recommendation to use a single range rule for large quantities; a Test number fea","domain":"learn.microsoft.com","publisherName":"Microsoft Learn"},{"title":"Prepare your organization's network for Teams","url":"https://learn.microsoft.com/en-us/microsoftteams/prepare-network","excerpt":null,"quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-09-14T00:00:00","supportsText":"Vendor documentation: per-endpoint bandwidth of 58 Kbps up and down recommended for audio, 2,500 Kbps up and 4,000 Kbps down recommended for meeting video; requirements are per endpoint, and one user on two devices counts as two endpoints.","domain":"learn.microsoft.com","publisherName":"Microsoft Learn"},{"title":"Site survivability for Webex Calling","url":"https://help.webex.com/en-us/article/d68vi1/Site-Survivability-for-Webex-Calling","excerpt":null,"quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-09-14T00:00:00","supportsText":"Vendor documentation: a local network gateway provides fallback calling to on-site endpoints when the connection to Webex is lost, with internal and external calls available during failover; external calling configured through a voice interface card or a SIP trunk to a PSTN gateway; port reference t","domain":"help.webex.com","publisherName":"Cisco Webex Help Center"},{"title":"47 CFR § 9.16: General obligations for direct 911 dialing, notification, and dispatchable location","url":"https://www.law.cornell.edu/cfr/text/47/9.16","excerpt":null,"quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-14T00:00:00","supportsText":"US rule: obligations on persons who install, manage or operate a multi-line telephone system to enable direct 911 dialing from any station with dialing facilities without a prefix, to configure notification where possible without hardware or software improvement, and to convey dispatchable location,","domain":"law.cornell.edu","publisherName":"Legal Information Institute, Cornell Law School"},{"title":"47 CFR 9.3, Definitions: Interconnected VoIP service","url":"https://www.law.cornell.edu/cfr/text/47/9.3","excerpt":null,"quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-14T00:00:00","supportsText":"US rule: multi-line telephone system defined to include network and premises based systems such as Centrex and VoIP as well as PBX, hybrid and key telephone systems; dispatchable location defined as the validated street address of the calling party plus additional information such as suite or apartm","domain":"law.cornell.edu","publisherName":"Legal Information Institute, Cornell Law School"},{"title":"How to Switch From On-Prem PBX","url":"https://sangoma.com/blog/how-to-switch-from-on-premises-pbx","excerpt":null,"quoteText":null,"sourceRole":"SUPPORTING","verifiedAt":"2026-09-14T00:00:00","supportsText":"Vendor migration guide (Sangoma sells communications platforms and services), published February 19, 2026: audit users, locations, devices, trunks, call flows and special-purpose lines such as fax, alarms and elevators; overlooked call scenarios named as fax lines, paging systems, door intercoms and","domain":"sangoma.com","publisherName":"Sangoma"},{"title":"On-Prem to Cloud VoIP Migration Guide","url":"https://tcinow.com/on-premise-to-cloud-voip-migration-guide","excerpt":null,"quoteText":null,"sourceRole":"SUPPORTING","verifiedAt":"2026-09-14T00:00:00","supportsText":"Provider and agency guide (TCI resells cloud voice services): auto-renewal windows often 30 to 90 days before contract end; PoE switches for desk phones, Quality of Service for voice traffic and firewall SIP handling checks; older analog phones may need an ATA; the page's own end-to-end figures of 2","domain":"tcinow.com","publisherName":"TCI"},{"title":"Porting","url":"https://support.ringcentral.com/porting.html","excerpt":null,"quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-09-14T00:00:00","supportsText":"Vendor documentation for its own porting process: transfers of more than 100 numbers from the same carrier are handled as project-based porting; the information collected at order creation covers the numbers, account number, account PIN or passcode and the registered physical address, with some carr","domain":"support.ringcentral.com","publisherName":"RingCentral Support"}],"revisions":[{"revisedAt":"2026-06-08T19:57:25.984+00:00","versionLabel":"Originally published","note":"","reviewedBy":null}],"relatedAnswers":[{"id":"f7b5d5d8-aadd-4135-b31d-5ff0dbbf934e","slug":"what-ucaas-deployment-model-suits-enterprises-with-hybrid-infrastructure","question":"What UCaaS deployment model suits enterprises with hybrid infrastructure?","publishedAt":"2026-09-27T14:29:18.879","confidenceScore":null,"confidenceLabel":null,"industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"ucaas","label":"UCaaS","description":null,"schemaKind":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"snippet":"For an enterprise with hybrid infrastructure, we'd recommend cloud call control, with equipment kept on site only where a named system, contract or outage requirement needs it. Coexistence, media routing and survivability are separate choices, shown with Teams Direct Routing and, as a separate service, Atlantech's hosted lines.","url":"/q/what-ucaas-deployment-model-suits-enterprises-with-hybrid-infrastructure"},{"id":"790feafe-8a6a-45e3-a954-23056b271d9a","slug":"how-does-ucaas-compare-to-on-premises-pbx","question":"How does UCaaS compare to on-premises PBX?","publishedAt":"2026-09-07T19:54:51.173","confidenceScore":null,"confidenceLabel":null,"industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"ucaas","label":"UCaaS","description":null,"schemaKind":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"snippet":"UCaaS and an on-premises PBX do the same calling job in different places. A PBX is equipment at your site that your team or a contractor maintains. UCaaS runs in the provider's cloud for a per-user monthly fee and adds video, chat and mobile apps. Cost, upkeep, outage exposure and control of data all follow from that difference, and a business can keep its PBX while changing the service that feeds it.","url":"/q/how-does-ucaas-compare-to-on-premises-pbx"},{"id":"62173c10-e3cc-4a28-bec3-67d899f7f24f","slug":"how-do-you-evaluate-ucaas-providers-before-buying","question":"How do you evaluate UCaaS providers before buying?","publishedAt":"2026-09-03T14:28:51.344","confidenceScore":86,"confidenceLabel":"High","industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"ucaas","label":"UCaaS","description":null,"schemaKind":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"snippet":"Evaluate a UCaaS provider in three passes: rule out providers that fail a fixed requirement, compare the rest on written price, term and service terms, then test your own call flow on your own equipment before signing.","url":"/q/how-do-you-evaluate-ucaas-providers-before-buying"},{"id":"a94ef24e-8f5b-40e8-9b5d-ec273215a8c8","slug":"what-ucaas-compliance-requirements-apply-to-healthcare-organizations","question":"What UCaaS compliance requirements apply to healthcare organizations?","publishedAt":"2026-08-25T14:28:52.466","confidenceScore":null,"confidenceLabel":null,"industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"ucaas","label":"UCaaS","description":null,"schemaKind":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"snippet":"In the United States, HIPAA sets the main requirements. A covered entity using UCaaS has to include it in its Security Rule risk analysis and safeguards, and needs a business associate agreement before using features that store patient information, such as voicemail, recordings and transcripts. HHS's Office for Civil Rights doesn't endorse or certify products.","url":"/q/what-ucaas-compliance-requirements-apply-to-healthcare-organizations"}],"contributorStats":{"verifiedAnswers":149,"openDisputes":0},"schemaJson":{"@context":"https://schema.org","@type":"Question","name":"How do you migrate from on-premises PBX to UCaaS?","text":"How do you migrate from on-premises PBX to UCaaS?","url":"https://www.answerstack.io/q/how-do-you-migrate-from-on-premises-pbx-to-ucaas","answerCount":1,"datePublished":"2026-05-05T19:57:25.984","about":[{"@type":"Thing","name":"UCaaS"},{"@type":"Thing","name":"Telecommunications"}],"acceptedAnswer":{"@type":"Answer","text":"You migrate by building the new phone system next to the old one, then moving your phone numbers across on a date the old carrier has confirmed. The number move is called a port. Its date depends on the carrier you're leaving, and undoing it means porting again, so the plan is arranged around it. Take inventory first, build and try the new system before the port, test inbound calls right after it, and cancel the old service last.","url":"https://www.answerstack.io/q/how-do-you-migrate-from-on-premises-pbx-to-ucaas","upvoteCount":0,"datePublished":"2026-05-05T19:57:25.984","dateModified":"2026-09-14T00:00:00","citation":[{"@type":"CreativeWork","name":"47 CFR 52.35, Porting intervals","url":"https://www.law.cornell.edu/cfr/text/47/52.35"},{"@type":"CreativeWork","name":"47 CFR 52.36 Standard data fields for simple port order processing","url":"https://www.law.cornell.edu/cfr/text/47/52.36"},{"@type":"CreativeWork","name":"Local Number Portability Porting Interval and Validation Requirements, Report and Order (FCC 10-85)","url":"https://docs.fcc.gov/public/attachments/FCC-10-85A1.pdf"},{"@type":"CreativeWork","name":"LNPA WG Best Practice 67: Processing Interval for Simple, Non-Simple, Porting Project and Customer Service Records","url":"https://docs.fcc.gov/public/attachments/DOC-309681A1.pdf"},{"@type":"CreativeWork","name":"Microsoft - Port phone numbers overview","url":"https://learn.microsoft.com/en-us/microsoftteams/phone-number-calling-plans/port-order-overview"},{"@type":"CreativeWork","name":"Transfer phone numbers to Microsoft Teams - Microsoft Teams","url":"https://learn.microsoft.com/en-us/microsoftteams/phone-number-calling-plans/transfer-phone-numbers-to-teams"},{"@type":"CreativeWork","name":"Country/region availability - Audio Conferencing, Calling Plans - Microsoft Teams","url":"https://learn.microsoft.com/en-us/microsoftteams/calling-plan-overview"},{"@type":"CreativeWork","name":"Plan Direct Routing - Microsoft Teams","url":"https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan"},{"@type":"CreativeWork","name":"Set up an auto attendant","url":"https://learn.microsoft.com/en-us/microsoftteams/create-a-phone-system-auto-attendant"},{"@type":"CreativeWork","name":"Route calls to unassigned numbers","url":"https://learn.microsoft.com/en-us/microsoftteams/routing-calls-to-unassigned-numbers"},{"@type":"CreativeWork","name":"Prepare your organization's network for Teams","url":"https://learn.microsoft.com/en-us/microsoftteams/prepare-network"},{"@type":"CreativeWork","name":"Site survivability for Webex Calling","url":"https://help.webex.com/en-us/article/d68vi1/Site-Survivability-for-Webex-Calling"},{"@type":"CreativeWork","name":"47 CFR § 9.16: General obligations for direct 911 dialing, notification, and dispatchable location","url":"https://www.law.cornell.edu/cfr/text/47/9.16"},{"@type":"CreativeWork","name":"47 CFR 9.3, Definitions: Interconnected VoIP service","url":"https://www.law.cornell.edu/cfr/text/47/9.3"},{"@type":"CreativeWork","name":"How to Switch From On-Prem PBX","url":"https://sangoma.com/blog/how-to-switch-from-on-premises-pbx"},{"@type":"CreativeWork","name":"On-Prem to Cloud VoIP Migration Guide","url":"https://tcinow.com/on-premise-to-cloud-voip-migration-guide"},{"@type":"CreativeWork","name":"Porting","url":"https://support.ringcentral.com/porting.html"}]}}}