I have an Imate K-jam, all the bars signal are present, but when others try to call me my phone don,t receive the call and my friends say that hear a message "is not powered on or is out of region " , to correct this i need to power off and on again to work for 2 or 3 hours and then the same problem apear again, i already try to make a hard reset and uninstall skype, backgamon and antivirus with no success.

please help !