Hi,

You need to hard reset your phone.

Before you do this make sure that the battery is fully charged.

Warning : A hard reset will restore your phone to factory default. You will lose all downloaded apps and user data!

To perform a hard reset do the following:

1.Turn off your phone

2. Press and hold the Volume Up + Power button (both together) until you see Recovery mode.

3. Release both buttons.

4. Select option "wipe data/factory reset" from the menu.

(To scroll options use Volume buttons, and to confirm press Volume Up key for 3 seconds).

5. Then confirm "yes" by Volume Up.

6. In the end accept (confirm with Volume Up key) operation "reboot system now"

The phone should now reset, be patient it takes a few minutes.