Microsoft Teams has a number of Features/Side bar buttons that are shown or hidden depending on the features a user has enabled.
By default you have
Microsoft sometimes calls these “apps”.
By default a Teams user can make VoIP calls, they are made via chat, the calling button is top right
However, now VoIP enabled Teams users will see the Calls button:
Presumably without the dial pad.
The calls app was previously removed for VoIP users in January as they were seeing clickable PSTN numbers and trying to dial them. I also would assume this is now fixed.