Do a factory reset:
> Settings
> Backup and Reset
> Factory Data reset.
or
> Turn off your device.
> Next, hold down the Home, Power, and Volume Up button all together for few seconds till Android logo appears on the screen.
> Release the buttons then the use volume down button for highlighting any options and Power key to confirm it. Highlight the factory reset option and confirm it using the power button.
> Next, select ‘Delete all user data’ and confirm it.
Wait for few seconds to see the ‘Reboot system now’ option and select it. The phone will be restarted then and you need to set it up.