Here are Some simple steps!
1. Turn off your device
2. press Up Volume key and hold it.
3. Now press Power button and hold it.
4. It will open a secret Terminal.
5. Use home button to go up and down.
6. Use Delete ALL USER DATA
7. It will take some time, and problem is solved.
WARNING: if you use this trick the data of your device will be lost but your phone will unlocked !!!