Are you setting a lock policy for your Teams desk phones? I get the risks of not locking and protecting calendar and contact data, but the unlock process is troublesome for end users.
Would be nice to be able to disable Calendar from the desk phones when policy is UserSignIn. Also, would be cool if only speed dials were listed for People/Contacts and are only read only driven by the config on Teams desktop app. I have tinkered with setting the phone as commonarea phone for a normal user but the UI was to restricted as contacts were limited.
Went live with Teams voice on 3/15 with a small org <50. Have about 16 using a desk phone and others using desktop or iOS app. Previously used Cisco call manager and Unity with 7940 and 7960 desk phones.