Why do Calls to this device get picked up by other devices?

1. Go to the phone menu and select settings, select Calling accounts and then tap on the SIM card.
2. In this screen scroll down and select “Call Forwarding”.
3. And then Voice, check if the “Always forward” option is enabled, if this is the case disable. In this screen there are three further options “forward when busy”, “Forward when unanswered” and “Forward when un reachable”.
4. Enable/Disable the functionality you desire.