To make a call, tap Calls > and enter a phone number. If you’ve enabled the setting to allow access to your phone contacts, tap Calls > Contacts and select the person you want to call. Use the dial pad on your mobile device to dial numbers from your personal phone number and to make emergency calls to your country-specific emergency number.
You can start calls from one-on-one or group chats: From your chat list, tap New message and enter a name or names. From a chat, tap Video call or Audio call . The person you're calling can answer from their desktop or mobile app. You can also start a call from someone's profile card. Open it by tapping their profile picture in a channel or from a search.