1. Tap on the Chat menu icon on top right side corner.
2. Choose a conversation from your Recent Chat conversations.
3. Click on the name you want to send a message to or click add button on to create new chat message.
4. Tap on call button to start call the user, you can choose start call as Voice call, or Video call
5. Your call will established once the user answer your call.
This feature only available for Android users, and soon will rollout for IOS users in next incoming updates.