Microsoft Teams PSTN calling and conferencing

Understanding Microsoft Teams PSTN Calling and Conferencing

Teams has become the leading business collaboration tool on the market. Our own research shows that it’s used by more than 70% of large organisations, and 60% of businesses overall. Teams provides a seamless communication experience for chat, file-sharing and video/audio calls with other Teams users. But if you want to place a phone call, to an actual phone number, things get a little more complex. 

What is PSTN?

For most of us, PSTN is a term you’ve heard, yet know very little about. PSTN stands for “Public Switched Telephone Network”, and is sometimes called the “Plain Old Telephone Service”, or POTS. It’s the normal phone network. 

Digital tools, like Teams, can be connected to the PSTN using integration technology like SIP Trunks and an IP-enabled PBX (Private Branch Exchange). But what you really need to know is that if you’re calling a phone number, that call is likely being placed through the PSTN (at some point) — whether or not you’re calling on a digital device or a traditional telephone. 

Why is PSTN calling important? 

The ability to place a phone call is one of the most underrated (and under-noticed) communication channels in modern business. The dramatic shift towards remote working in 2020 has exposed challenges providing access to business phone systems. However, the need to place a phone call is simply an important facet of communication that most business collaboration tools entirely ignore. Particularly when communicating with external stakeholders, it’s an important component to get right. 

Part of what distinguishes Microsoft Teams as a leading collaboration tool is the number of options you have to place a standard phone call (PSTN call) with the platform. Here, we are going to explain these options, and how you can place a phone call with Teams today. Let’s get started. 

How to set up PSTN calling with Teams

PSTN calling does not come standard with your Teams or Microsoft 365 licence. There are Microsoft options for integrating this capability within Teams. However, there are third-party alternatives that may serve you better. 

Option 1: Cross launch apps

A number of calling apps, for example, RingCentral, Cisco Jabber and Zoom all provide PSTN calling capabilities accessible from Teams through software overlays and quick launch options. At first glance, this is a simple solution. But it isn’t true integrated calling. 

Using cross-launch apps, you can initiate a call from Teams, but another application makes that call. Incoming calls won’t ring the Teams client, they ring in the third-party app. This creates a disjointed workflow and prevents any integrated conferencing capabilities. This might be something worth experimenting with on a limited basis, but it’s not a solution that we can recommend. 

Option 2: Microsoft Phone System and Calling Plan

Microsoft’s solution to PSTN calling with Teams is Phone System and Calling Plan. Phone System is a licencing requirement, and a control tool that provides basic call management functionality. 

Effectively, Phone System is the gateway to all integrating calls with Teams, but doesn’t actually provide that much on its own. Phone System is included with Microsoft 365 E5, but otherwise needs to be purchased separately. This diagram shows those options in relationship to Direct Routing.   

Microsoft Teams Calling - License Diagram

Check out our blog about Microsoft Phone System if you want to learn more about both Calling Plan, Phone System and making calls with teams. 

To actually place calls with Teams, you need Calling Plan — which has a number of pricing and minute package options, including both domestic and international calling. Again, there are a number of ways to purchase this solution, check out the blog below for details. 

Suggested reading: Microsoft Teams Calling Plan Pricing Explained.

Calling Plan and Phone System will deliver a fully integrated outcome. You get federated presence, centralisation of data, and one tool for all communication. The problem with this solution is that Phone System isn’t a sophisticated control tool. Traditional corporate “phone systems” (note the lack of capitalised) control calling with a PBX (Private Brand Exchange) and/or SBC (Session Border Controller). Microsoft compares Phone System to a PBX, but you won’t get the same level of control. For example. Phone System does not provide: 


      • Call recording: Which can be a problem for compliance and training. 

      • Individual call reporting: Which can make it hard to control individual users and usages. 

      • Poor call queue management: Which can make managing a large volume of calls challenging. 

    Fundamentally, businesses will find it hard to replace their existing phone system with Microsoft Phone System. This option will let you place PSTN calls, and engage in conference calls, but it’s unlikely to entirely unify your communications system. 

    Option 3: Direct Routing

    Direct Routing allows you to integrate Teams with PSTN calling and provide a fully-functional business telephony system. However, this means looking beyond Microsoft to get the job done.

    Realistically, there are as many types of “Direct Routing” as there are Direct Routing suppliers. However, in general, Direct Routing delivers:


        • Complete PBX control: You can manage Teams calling like a standard phone system. You get the reporting, cost control and queue management tools required to handle any calling environment.

        • Endpoint and handset flexibility: You can keep your existing hardware, embrace BYOD and invest in the right tools for the job. Microsoft Phone System limits your choice to select supported handsets. 

        • Unified communication: You have complete access to call records and contacts, a single sign-in point for all communication, and federated presence across all devices and channels.

        • Reduced costs: The right provider can deliver Direct Routing at less cost than Microsoft Calling Plan. 

      Full disclosure: We provide one of these “third-party” solutions — Callroute — and can get you up and running in minutes with a free channel for life, and provide flexible per-channel pricing. Our tool was built to enable users to replace their phone system with Teams, and get the most out of business collaboration. Get in touch if you want to start calling with Teams today.

      Suggested reading: What is Direct Routing?

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      How to set up PSTN conferencing with Teams

      No matter which option you chose for general PSTN calling capabilities with Teams, conference calls are done the same way — you just need an Audio Conferencing licence. Again, this is included in Microsoft 365 E5, but otherwise has to be purchased separately. There are pay-per-minute options, however, it’s likely more effective to get a licence from £3 per-user/per-month.  

      To work, an Audio Conferencing licence is only needed by the meeting host. When activated, it assigns a toll (or toll-free) number to users who have the option to dial into that meeting from their phone. If you have a Direct Routing solution, this call could actually be placed by Teams. Either way, it provides a PSTN bridge to the conference call. 

      Once enabled, you can effectively just use the option like you would with other meeting setups within Teams. Users can join the conference meeting from Teams, from a calendar link, or dial in using the number provided in the invite. 

      Pro-Tip: If you have a Direct Routing solution and an Audio Conferencing licence, users can set up “On-network Audio Conferencing”. When appropriately configured, this routes the dial-in options through your own network — reducing costs. However, this is only available to internal users, not third-party dial-in numbers. 

      How to start calling today?

      If you want to replace your standard PSTN phone system with Teams, and centralise your communication on a single collaboration platform, you need Direct Routing. This will enable you to place and receive PSTN calls from Teams just like you would using legacy endpoints and handsets. Adding an Audio Conferencing licence then enables full flexibility to call external users directly, or include them within broader Teams-based conferencing. 

      Teams has the potential to be the only communication tool your business needs. But in order to make that a reality, you need to integrate fully-functional PSTN calling and conferencing capabilities. Direct Routing can deliver that solution. You need to choose the option that’s right for you. At Callroute, we can get you up and running with a free channel for life in minutes. You just need to be a Teams user and have a Microsoft Phone System licence — we take care of the rest, including number porting and 24/7 customer support. Try it out free, and then scale up the number of channels after you see the results.

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      Intermittent Microsoft Teams calling issues reported globally. This issue appears to be affecting all Microsoft customers worldwide. Microsoft are currently investigating the issue. All Callroute systems are fully operational. More information will be provided as soon as possible.