First, turn your phone off, wait for a couple minutes and on it again. If you find this worked then the error happened with the software. It can be resolved by doing the power-cycling.

Second, remove the battery and sim card if you have one, while the phone is still in a turn on position. Wait for a couple minutes and put the battery and sim card back. Restart the phone and check the result.

Also check on Here and here is more Support for your phone. Good Luck and let us know what happened