What if your phone just says PUK blocked what do you do?

If it says "Enter PUK" or something like that. It needs a code from a service dealer or if your phone ISNT prepaid, you can go to at&t online. Log in, go into services, and get your PUK code to unlock your phone. PUK is like a theft lock, helps prevent thieves from taking your phone. If you get it wrong 10 times, it permanently locks your SIM card. If its permanently locked, you gotta go to a retail store from your provider and get a new SIM card. If your on prepaid phone, you gotta get tech support to help you unlock your phone or at a store as well. Tech Support: 1-800-901-9878 for AT&T Prepaid.