How do I choose a PSTN connectivity option for Teams Phone?

All four options do the same job. Each one connects Teams Phone to the public switched telephone network, or PSTN, and brings phone numbers into your tenant. Every user has to be licensed for Teams Phone whichever one you pick. The options differ in who the operator is and who manages the link.

With a Calling Plan, Microsoft is the operator, so the numbers, the network access and the support all come from the company that already runs your Teams. Microsoft's comparison calls it the fit for organizations that want a fully Microsoft-managed service with the simplest deployment.

Availability decides whether it's on your list at all. Microsoft sells Calling Plans in some countries and regions, and it points you to the other routes where it doesn't. So look up your users' countries before deciding whether you need a Calling Plan.

Operator Connect puts a phone company in Microsoft's place as the carrier. Microsoft recommends it when you want a managed connection without running your own session border controllers, or when you want to stay with a phone company that offers it. A session border controller, or SBC, is the device that sits between a carrier's network and Teams.

Under Operator Connect, Microsoft is responsible for Teams and its admin center. The operator is responsible for PSTN connectivity, for providing and porting numbers, for the calling service and for support on all of those. You enable the operator in the Teams admin center and assign its numbers to users there.

Operators aren't interchangeable, so the choice continues inside this option. Microsoft suggests comparing them on country coverage, number availability and porting support, service offerings and any relationship you already have. Pricing models differ too, and Atlantech Online's Operator Connect page shows two of them. The first is a flat rate "as low as $3 per user/month," with unlimited US calling and number porting listed. The second charges a small per-user cost plus a shared pool of PSTN capacity. Atlantech describes that one as suited to organizations of 500 or more users where only a fraction are on a call at once.

The two models put the cost in different units, so which one is easier to budget depends on how many of your users are on outside calls at the same moment. Atlantech publishes no rate for the shared model, so that side of the comparison needs a quote. Ask for both quotes on the same user count and the same peak number of calls, so the two can be compared.

Both prices are for the carrier's service. Microsoft licensing is separate, and users who already have Teams Phone through an existing subscription don't need it again.

Teams Phone Mobile is meant for mobile-first employees, such as field workers and sales representatives, who should have a single business number. That number is the one on a company-provided SIM. The user can make and receive calls on it through the phone's own dialer or through Teams.

The mobile operator has to take part in the program in the countries where you need it. Teams Phone Mobile also supports user numbers only, so it can't carry the number for an auto attendant, a call queue or a conference bridge. A company that picks it for field staff still needs another route for a main line answered by an auto attendant or a queue.

Direct Routing suits a particular set of cases: an existing carrier relationship you want to keep, a third-party PBX or analog devices that have to stay connected, advanced call routing, and deployments that span several countries. You use the carrier you choose, because the link is an SBC connected to Teams.

The SBC brings work of its own. It has to be a model Microsoft has certified, and it needs DNS records, certificates and firewall rules of its own. You don't have to own or run the device yourself. Microsoft allows it to be procured, installed and managed by you, by your integrator or by a hosted Direct Routing provider. So the question to settle is who operates the SBC and who answers when a call fails.

Atlantech's explanation of Operator Connect states the trade from a carrier's point of view. Operator Connect removes the work of managing SBCs. In exchange, you give up some control over call routing, customization and integration with older systems. That control matters when you have a PBX to keep in service or routing rules particular to your business, and Direct Routing is the route built for those cases. That trade is one difference between Direct Routing and Operator Connect.

Emergency calling is one place the difference shows up in setup. Direct Routing requires you to configure specific call routing policies for emergency calls. With the other options, the carrier handles much of that configuration.

One tenant can run several routes at once, assigned by user or by location. Microsoft gives an example of Teams Phone Mobile for mobile workers, Operator Connect for knowledge workers and Direct Routing for workers in remote regions.

Suppose a company has 120 people in the United States. Ninety work at desks, 20 are field technicians with company phones, and ten work in a warehouse that still has an older PBX and an overhead paging system. The desk workers can go on Operator Connect with the company's current carrier, if that carrier is in the program. The technicians can use Teams Phone Mobile, if their mobile operator participates. Assume the warehouse's PBX and paging equipment can be connected through a certified SBC. Then the warehouse can use Direct Routing and keep them in service. All 120 are on the same Teams Phone system, and each has to be licensed for Teams Phone, which some may already be through their existing Microsoft subscription.

Price doesn't sort the options in a fixed order. The total depends on the quotes you get and on how much your users call, so compare routes using the same users and the same calling pattern. Add the Microsoft licensing to each route to see what Teams Phone costs in full.

The first choice also doesn't lock in the rest. Microsoft lets you add and manage these connections over time, in any order. A company can start every user on the simplest route available to it and add a different route for specific groups later, once it knows which of them need something else.