Before you start pulling the trigger on moving a bunch of your Phone System users over to using Microsoft Teams as their primary calling client (instead of Skype for Business), there are several caveats that you need to be aware of. I made a brief tutorial/demo video that goes into detail on these caveats, and really helps explain what they mean for Phone System users.
You can follow this link for more info and a demo, or watch the video below (following the link takes you to YouTube, where you can watch the video in a larger frame):
I hope you find the video insightful and useful, and if you have any feedback or suggestions about how these videos could be better, please don't hesitate to let me know. I will be releasing more of these as Microsoft gradually releases more of these roadmap features over the next 12 months!