Call a phone number from Teams

To dial a number from Teams, go to Calls  , click Dial a number, and then enter the number of the person you want to reach. This way you can contact anyone, even if they're outside your organization.

In the Calls  area, you can also access favorite and suggested contacts, listen to your voicemail, and check your call history.

Call a phone number from Teams (mobile app)

To make a call, tap Calls  > Dial pad  and enter a phone number. If you’ve enabled the setting to allow access to your phone contacts, tap Calls  > Contacts  and select a contact.

Source:

https://support.office.com/en-us/article/call-a-phone-number-from-teams-20d24ace-2851-4c29-8441-30dd2a5cf078