Using Boss-Admin

Bosses can share their phone line with their assistants|delegates to make and receive calls on their behalf.

See here a video clip showing how to set up the feature. The principle is the same across all Teams phone models.

A boss can:

View and join active calls handled by delegates as a boss
Grant delegates permission to join active calls and resume calls

A delegate can:

View shared call history per boss' line
Switch between different lines easily
View other delegates managing a boss
To set up the feature:
Use the screenshots below as reference.