galaxy s3 locked in error by Android device manager

A

AC Question

Tried a number of time to unlock the phone by entering the pin as instructed in the website. I have done this so many times is not even funny anymore! I think my only way to be able to use the phone again is to erase the data but I would like to know if once I have lost all of the data if I will be able to reuse the phone.
Could I use an old sim to do the erase process?
I keep on going round in circles and getting nowhere!
Thanks