Factory reset sounds like the solution your looking for.
'''Caution this will delete any data on your device'''
'''Hard Reset'''
Switch off your device.
Press and hold the following keys at the same time: Power/Lock Key + Volume Down Key.
Release the Power/Lock Key and Volume down Key when you see the Factory Hard Reset screen.
Press the Power/Lock Key to confirm (or press any other key to cancel). When you press the Power/Lock Key to confirm, the message "Are you sure you want to continue with erase?" is displayed.
Press the Power/Lock Key and your phone will be restored to the factory settings. To cancel, press the Volume Keys.