Reset your phone.
Warning: Resetting your phone erases all personal content, including apps, and restores the factory settings.
- Make sure the charger is disconnected, and switch the phone off.
- Press and hold the volume down key, and connect the charger. An exclamation mark (!) is shown on the screen.
- Press the keys in the following order: volume up, volume down, power, and volume down. Your phone resets and boots up. This may take several minutes.