With chat, you can have private one-on-one or group conversations that are not in the public team channel. And with calls, you can make calls or check your history or voicemail.
.
or Audio call
to call someone directly from a chat.On the left side of the app, you’ll see your Recent conversations as well as your Favorites.
Note: If your organization has an Enterprise Voice license, you can call anyone from Teams even if they’re not using it.