We spent the best part of 2 weeks being batted backwards and forwards between O2 and Samsung with everybody listening in confusion as though they had never encountered such a thing as a frozen phone. We had the same NUC code ad nauseum from O2 which never worked. They had no idea what to do next and are still cogitating about how to wriggle out of this problem. We contacted Simply Unlocked and within 3 hours they had sent down the correct codes with simple instructions on how to unlock the phone. It worked perfectly and within 5 minutes the phone was unlocked and working. I cannot recommend them highly enough! Well done. It really does work.