If you have forgotten your PIN to unlock your phone, firstly, do not keep guessing as you will lock the sim, too. Resetting your device will also have no effect. The only way to unlock your phone if you have forgotten your pin is to enter the PUK code found on the plastic card your sim came from. If you do not have this, contact your provider and they will tell you. You will then use this PUK to create a new PIN code to use from now on.