Voicemail is not turned by default in Teams, but it’s easy as 1-2-3 to turn on and customize!
1 – In Teams, open Settings and More from the top bar

2 – From the Settings menu, select Calls

3 – Under “When you can’t answer a call”, select the option “Redirect to voicemail”

Scroll down to the Manage Voicemail section to record a greeting and set other options.
See Microsoft’s Manage your call settings in Teams for additional information.