Hard Resetting will deletes ALL personal data and settings and restores your phone to factory default conditions as if you turned on the phone for the first time after purchasing.
Please follow the step :
1. With the device turned off, press and hold the VOLUME UP and VOLUME DOWN buttons, then briefly press the POWER button.
2. Continue pressing the VOLUME UP and VOLUME DOWN buttons until you see this message on the screen:
"This operation will delete all your personal data, and reset all settings to the manufacturer default settings. Press Vol Up to restore manufacturer defaults, or press other keys to cancel."
3. Release the VOLUME UP and VOLUME DOWN buttons.
4. Press the VOLUME UP button to perform the hard reset, or press any other button to cancel the reset.
You can also use Clear Storage to reset your device back to factory default settings.
1. On the Home screen, slide to the Settings tab and then tap Menu > All Settings.
2. On the System tab, tap Clear Storage.
3. Enter “1234” and then tap Yes.
Make sure you back up all your data such as Contacts, Appointments, messages etc or they will be gone forever.
wish you luck
:)