Here are a bunch of links that will probably help the most:
https://learn.microsoft.com/en-us/microsoftteams/enduser-training
https://learn.microsoft.com/en-us/microsoftteams/training-microsoft-teams-landing-page
Also, MVPs are a useful bunch. Here's a filtered list for current Office Apps MVPs:
https://mvp.microsoft.com/en-us/MvpSearch?ex=Office+Apps+%26+Services&sc=e
And many ex-MVPs (still just as clever, but maybe have more time to offer)
https://mvp.microsoft.com/en-us/MVPReconnectSearch?kw=teams&sc=f
All the best,
Pete
Hi arndh - this may get more attention by posting as a question as opposed to a reply, however I wanted to respond. Just tested using two commas after the number and it did not work on the desktop Teamsapplication. There is a User Voice page addressing it where you can vote for it and subscribe to updates.
https://microsoftteams.uservoice.com/forums/555103-public/suggestions/32977114-click-to-dial