To call the watch while in the App, press the Dial icon on the map screen to make a phone call to the watch. You can also create a contact in your phone with the watch mobile number and call the watch as you would call any other contact in your phone contact list. Or simply dial the watch mobile number from your phone once your phone number is included in the watch contact list.
Note: the watch sim card number has 3 more digits than a standard mobile number with the International codes, i.e. + and 15 digits. When calling the watch from the App, you are making a call from your mobile phone and are charged by your mobile operator for the call. Calls through the App are not free.