If the call is still ringing at the intended destination after it starts ringing at the other location, it is covering to that phone. If it is no longer ringing, it is forwarding. To eliminate the forwarding, go the phone that is fwding and dial #33 + ext number to forward calls back to itself. If it is covering, go to the phone that is receiving the unwanted calls and dial #00 and press all of the buttons to see if any have a Primary cover button of the intended phone. If they don't you will have to review the set in Centralized Programming or it could be done via Calling Group/Cover Group.