Turn off your phone. Next Press and Hold Home button + Volume Up + Power button (or) Volume Up + Power button (or) Volume Down + Power button (or) Volume Up + Volume Down + Power button Until you will see Android reboot menu. Then select option: “wipe data/factory reset” using Volume Down, and Power button to confirm operation. After that choose option “yes” with Volume Down, to select and Power button to accept. After that press Power button to enter option “reboot system now”. Success. Format done on your mobile.