When I try to make a phone call an error message pops up saying "Not Registered on Network". When I go into my settings and check the Mobile Networks I receive a message saying "Insert SIM Card to access network services" I tried removing the battery and SIM, turning the phone off and on, putting the battery and SIM back in and turning the phone back on and I can get the "SIM" message to go away, but the "Not Registered on Network" message will not go away... Please help!!! I have a SIM card and I've only had the phone for a few weeks!!