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 !!!