Blocked Google/Samsung phone

Hi there I have a google/Samsung which has worked perfectly til last week. I got up on Sunday to a message that my SIM card locked. I have called Mobistar, they are sending a new card, but it isnt a card issue as its the access code to log ino the phone. Also I have put a completely new card and number in and the same message appears. The whole phone is unusable as I cant get throught the security code. Does anyone know how to resolve this? I wonder if it may have something to do with a new update of the software that has appeared in the last week or two. Thanks