To place a call on hold, click More actions
in your call window and select Hold. Everyone in the call will be notified that they've been put on hold, and you can continue your call by clicking Resume.
People on hold (including you) won't be able to see or hear anyone else on the call. Screen sharing is temporarily suspended, too. Everything will return to normal once you resume your call.
Anyone who's on a PSTN line will hear music when they're put on hold.
To start the call again, click the Resume button in the toolbar.
Mobile
To place a call or meeting on hold, tap More options 
in your call window and select the hold option. To continue the call, tap Resume.
The articles below show a step by step guide on how to manage the calls setting on Microsoft Teams
Learn more about answering a call on Microsoft Teams.
Learn more about transferring a call on Microsoft Teams.
Learn more about managing your call settings on Microsoft Teams.