During a Teams call, you can take many actions. Here are a few common scenarios:
Place a call on hold
Select More actions 
in your call window and choose Hold. Everyone on the call will be notified that they've been put on hold. Continue your call by selecting Resume.
Transfer a call
Select More actions > Transfer in your call controls. Then, type in the name of the person you want to transfer the call to and select them. To finish, select Transfer.
Consult then transfer
If you want to check in with someone before you transfer a call to them, select More actions > Consult then transfer.
Under Choose a person to consult, start typing the name of the person you want to reach and select them when they appear. You can call them or consult with them over chat. When you're ready, select Transfer.
Add a delegate
You can select someone in Teams to be your delegate—to receive and make calls on your behalf. When you add a delegate, you’re sharing your phone line with them, so they can see and share all your calls.
To assign a delegate, select Settings and more 
next to your profile picture. Choose Settings > General. Under Delegation, select Manage delegates. There you'll see who you're a delegate for and add and remove your own delegates.
Share a line with a delegate
Select Settings and more next to your profile picture at the top of Teams and choose Settings > General. Under Delegation, select Manage delegates. Select Your delegates and type the person's name in the Add a delegate box.