Microsoft explains they have noticed “an increased number of users without Enterprise Voice licenses (odd language, the Office 365 Licence is “Phone System”) attempt to make PSTN calls.
This is occurring because these users can see clickable phone numbers in the Calling App.”
Microsoft has some internal language where they talk about the “left rail” where the difference function buttons are and the functions as “apps” e.g. calling. So this would be the calling app.
The Calls app provides PSTN dial pad for those who have Phone System licence. These users can make PSTN calls via Direct Routing or, in some countries, a Microsoft cloud calling plan. However, the calling app currently shows for everyone even if they don’t have the Phone System (the ability to make PSTN calls). The original logic of this was that you could still make user to user VoIP calls here. However, PSTN numbers are now being surfaced as clickable in the calls app, which leads users to believe they can make calls, and then seeing it fail.
So, for now, the calling app is being removed for non-Phone system users. Once all PSTN number entry points have been disabled, the Calls App will be re-enabled for all users. Microsoft anticipates that the Calls App will come back online near the end of March 2019.
Non Phone System users can still make calls from the chat app, which I expect is what most do anyway, so hopefully, this is not too disruptive for users. However, you should be aware this is quite a big visual change for users and will no doubt impact how some of them use Teams today.
I hope that we will have options in the future to show or hide specific apps. For example, if you just want meetings just to have the meetings app, or if you just want chat but not “Teams”, or any combination you want to choose for your enterprise.