Microsoft Teams calling - Direct Routing, Operator Connect or Calling Plans
Teams has become the phone system for a large share of enterprises, and there are three ways to give it a dial tone. How each works, what it costs to run, and which one fits a multi-country organisation with existing carrier relationships.
Three doors to the PSTN - Microsoft Teams Phone provides the call control, the client and the user experience, but it does not connect to the public telephone network on its own. Getting a Teams user a real phone number and the ability to call outside the organisation means choosing one of three PSTN connectivity models: Microsoft Calling Plans, Operator Connect, or Direct Routing. They are not mutually exclusive - many enterprises run two of them across different countries - but each has a distinct cost structure, a distinct set of countries where it works, and a distinct division of responsibility between you, Microsoft and a carrier.
Calling Plans - In this model Microsoft is your carrier. You buy a per-user calling plan licence, Microsoft allocates numbers and terminates the calls, and everything is configured in the Teams admin centre. It is the simplest option to stand up and requires no telephony infrastructure at all. Its limits are geographic and commercial. Calling Plans are available in a specific list of countries, and coverage in Asia Pacific, the Middle East, Africa and Latin America is thin. Pricing is per user per month with bundled minutes, which suits light users but becomes expensive for contact centres and heavy outbound teams, and international calling is charged at published rates rather than negotiated ones. You also cannot bring your existing carrier relationship, and porting existing numbers into Microsoft is a project of its own.
Operator Connect - Operator Connect keeps the simplicity of the Calling Plans experience but replaces Microsoft with a carrier of your choice from an approved list. The carrier peers directly with Microsoft's network over managed, redundant interconnects, and you assign the carrier's numbers to users from within the Teams admin centre. There is no SBC to run and no SIP trunk to configure on your side; the carrier owns the interconnect and the SLA. Commercially it is closer to a normal carrier agreement: you negotiate rates and number costs, and you can often bring existing numbers with the carrier handling the port. Operator Connect is the right default for most enterprises that want a carrier relationship without telephony infrastructure, and its country coverage depends on which carriers offer it where. The constraint is that the carrier must be an approved Operator Connect partner in that market, and functionality is limited to what the programme allows - you cannot, for example, insert your own SBC for call recording or route calls to a legacy PBX.
Direct Routing - Direct Routing is the most flexible and the most operationally demanding model. A certified Session Border Controller - on your premises, in your data centre, or hosted by a carrier - connects Teams to any SIP trunk from any carrier. That gives you complete freedom over which carrier serves which country, lets you keep an existing PBX or contact centre in the call path during migration, supports analogue devices and specialised endpoints via the SBC, and enables call recording, least-cost routing and custom dial plans. It works in every country where you can obtain SIP trunking and numbers, which is why it is the only viable option in many markets. The cost is that someone has to run the SBC: certificates, firmware, capacity, media bypass configuration, monitoring, and Microsoft's periodic changes to the interconnect requirements. Most enterprises resolve that by using a hosted or managed Direct Routing service, where the carrier runs the SBC on the enterprise's behalf.
Choosing for a multi-country organisation - The practical answer for most organisations spanning several regions is a mix. Where a good Operator Connect partner exists and there is no need for custom routing, use Operator Connect for its simplicity. Where you need SIP flexibility, legacy integration, contact-centre routing, or numbers in a country outside the Operator Connect footprint, use Direct Routing, ideally hosted, with a carrier that has local numbering and regulatory compliance in that country. Reserve Calling Plans for small user groups in countries where neither of the other models is worth setting up. Because all three coexist in one tenant, the decision can be made per country and revisited as coverage changes.
Questions to settle before you start - Which countries do users sit in, and where can each model actually deliver numbers with the correct emergency-calling and regulatory setup? Do you have numbers to port, and who will handle porting in each country? Do you need call recording for compliance, and where will it happen? Is there a contact centre, and does it need to stay on its existing platform for now? What is the total cost per user per month under each model when calling volumes are included, not just the licence? Who is on call when a trunk fails at 02:00, and what SLA covers it?
Where a carrier fits - A carrier that offers Operator Connect in the markets that support it, hosted Direct Routing everywhere else, numbers in 100-plus countries with local KYC handled, and a single contract and NOC across all of it removes most of the operational complexity that makes Teams telephony projects drag. That is the shape of the service that enterprises with more than a handful of countries end up asking for.
One migration principle - Move users in country-sized batches, keep the old system reachable until each batch has been through a full billing cycle, and put a real emergency-calling location record against every number before you enable outbound. Teams makes the user-facing part of the migration easy; the telephony underneath is still telephony, and it rewards the same discipline it always has.
