Microsoft Teams gives the user the ability to make voice only calls or video calls to another Teams user. These are direct calls and not part of a meeting or any other conversation in Teams. To access this feature, click on the calls tab on the task bar to the left. 

Here you can access the following features:

• Speed Dial
• Contacts
• History
• Voicemail

You will need to add the contact to conduct a phone call from here.

Note: Depending on your license, you may only be able to make calls to other Teams users. You may not be able to dial an actual phone number.