To transfer a call:
Choose More actions > Transfer in your call controls.
Start typing the name of the person you want to transfer the call to and select them when they appear.
If they're in your org and using Teams or Skype for Business, you can turn on Ring back if there's no answer. This will send the call back to you if the recipient doesn't answer.
To finish, hit Transfer again.
For more transfer options, click the drop-down arrow in the Transfer button. Choose Work to transfer the call to their Teams number, or Work voicemail to send it straight to their voicemail. If they've added any other phone numbers to their account, like their mobile number, you'll see those options in the list, too.
Just keep in mind you can only transfer calls when you're talking one-on-one.
If you want to check in with someone before you transfer a call to them, follow these steps:
When you're in a call, 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, hit Transfer.
For more information on call forwarding and simultaneous ring, please refer to the below articles.
Learn more about answering calls on Microsoft Teams
Learn more about calls forwarding to a call group on Microsoft Teams