On Dec. 12, Microsoft began to roll out support for some of the advanced calling capabilities that previously were only in Skype for Business to its Microsoft Teams service.
From Microsoft's Tech Community blog post:
"Today we are releasing new calling capabilities in Teams, providing full featured dialing capabilities, complete with call history, hold/resume, speed dial, transfer, forwarding, caller ID masking, extension dialing, multi-call handling, simultaneous ringing, voicemail, and text telephone (TTY) support. You can expect this to roll out over the next few hours and should come soon to your tenant."
To add calling to Teams, administrators need Phone System (the feature previously known as Cloud PBX), which is part of Office 365 and also available as an add-on for other Office 365 plan users. At that point, users can subscribe to a Calling Plan -- what was formerly known as PSTN Calling.
While many enterprise-grade calling features aren't coming to Teams until the end of Q2 2018, a few like call parking, group call pickup, location-based routing, and shared-line appearance are not going to be there until Q4 2018. Call support between Teams and Skype Consumer is a Q2 2018 deliverable, officials said earlier this year.