Cause 8 of 14: The phone is overloaded for unknown causes
If your phone is overloaded, you can't make any calls. It may help restarting it.
Solution: Restart your phone.
Restart your phone
Open the Reset key cover.
Restart your phone
Press and hold the Reset key with a sharp-pointed object (such as a paper clip) until your phone turns off.
Restart your phone
Close the cover again.
Restart your phone
Press and hold On/Off until your phone is turned on.