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With lockdown easing, you’ve probably all had a long few months configuring Microsoft Teams, Zoom and a whole host of other remote-working functionality for your clients. How about expanding the Teams platform to your clients to allow them to either use Teams as their PBX or bond the two platforms together. Let’s take a look at how it’s done!


Before we get into Direct Routing, I’d like to explain some prerequisites you will need and also another option that you can use that require far less configuration, but also lack in functionality in comparison.

Microsoft Phone System License

So regardless of if you opt for Direct Routing or Calling Plans, you’re going to need a Microsoft Phone System license (or Business Voice*). This license will enable Enterprise Voice for your users and each user that requires a telephone number will require this license. At the time of writing, the license is around £6/user/month.

*The Microsoft Phone System license is only available to Enterprise customers on E1, E3 or other licenses like A3 Faculty. If you’re using licenses such as Microsoft Office 365 Business Standard, You’re going to need a ‘Microsoft 365 Business Voice’ license.

Calling Plans

So when it comes to calling plans, you’re basically opting to keep your PSTN functionality with Microsoft and not your existing provider (or a 3rd party). You can choose from a Domestic Calling Plan or Domestic & International Calling Plan costing around $12 vs $24 – This is on-top of your Microsoft Phone System or Business Voice license.


Microsoft Calling Plans including the Business Voice with Calling Plan now includes 1,200 pooled minutes per user. These are pooled at tenant-level and shared collectively across all Enterprise Voice users.

Call Costs

I’ve taken the time to get a list of call costs below from Microsoft when using Calling Plans. The first Spreadsheet is UK-Based costs, and the second option is US-Based. If you previously had Enterprise Voice on Skype for Business they will likely be the same price-range.

Direct Routing

So we’ve seen the costs for Calling Plans, but what about Direct Routing? Well, it’s not something I can give you explicitly, as they rely on the Certified Partners. At the time of writing, the list contained:

  • AudioCodes
  • Ribbon
  • Thinktel
  • Oracle
  • Cisco
  • TE-Systems
  • Metaswitch

The process involves using a Session Border Controller (SBC) either virtually or physically and routing calls from your PSTN to Teams and back. Costs are likely to be less than using a Calling Plan and includes more functionality but also means that you have some infrastructure in the middle that you or the SBC provider has to manage.


As the products go, I prefer Direct Routing with an SBC rather than a Calling Plan. You can set a Calling Plan up with much less work, but you’ll pay through the nose for it. Using an SBC also gets around some known Teams limitations for anybody using it as their PBX as we’ll describe below. If you can, invest in the SBC route and training and you’ll benefit from it long-term.

Certified Handsets

Personally, I’ve only used the YeaLink T55A Teams Phone which I think is great. It’s quite an expensive handset if you’re looking for Communal phones or need to replace every phone for a client or yourselves. As a handset, you need to only provide it power and network (PoE ideally) and sign in using the touch-screen on screen keyboard to get going. (Ensure you have Enterprise Voice enabled first for your users)

Known Limitations

I’ve been using Teams and these functions for months now and have compiled a list of my ‘known’ issues and limitations, there may well be more out there, but here’s what I’ve found.

  • No ‘Internal Extension’ – Calling a colleague using their DDI will be an external call using an E.164 number, this means that you’re paying using your normal call rates unless using a certified Microsoft Teams desk-phone.
  • No CLIP Modification – It isn’t currently possible using Calling Plans to modify the number that you’re calling out from. Your options are to use a service number from Microsoft, Your DDI number or to hide your caller ID completely.
  • Number Porting – Porting your number into Microsoft Teams using Calling Plans is an awful process including Letters of Authorisation and jumping through hoops to get your numbers imported.

Final Thoughts

I think it’s incredible to see how far Microsoft Teams has come and is still making huge steps towards replacing software like Slack and Skype for Business. It’s still not 100% as a platform but it’s making progress each day. If you would like a guide on the actual configuration of any modules discussed today, please reach out to me and let me know. If there is enough interest I will make some documentation.



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