If there is no hardware issue, factory reset should resolve all problems that you have with your phone. If you have important files on your phone (pictures, videos etc.) back up your files to the computer before performing factory reset.
Factory reset procedure:
1. From the main screen, press the "Menu".
2. Press the "Settings" > Phone > Reset Settings > Master Reset
3. "All settings will be reset. Continue?" will be displayed. To confirm, press "Yes."
4. You will be prompted to enter your security code; please enter your 4-digit security code (default code is 0000, 1234 or last 4 numbers of your phone) then press "OK." "Resetting" will appear then "Done," when finished.
5. You will be prompted to tap the center of the cross on the screen several times to calibrate the touchpad; please follow the directions on the screen to calibrate the touchpad.
6. "Save touchpad Calibration?" will be displayed. To save, press "Yes."