I just called Apple to ask them to review over my situation, because the same thing is happening to people from different countries. after their carriers unlocked their phones their are getting the SIM Not Valid message
I talked to the most negative and negligent Senior Advisor that Apple may had hired, a jerk named Jeffrey.
While i was trying to explain him the situation he only could tell me APPLE CANT UNLOCK YOU PHONE. and i told him 100 times my phone is already unlocked from AT&T and i am not asking you to do that.
what a torture to deal with such a lazy person.
The fact is that after my investigation, i have noticed that iphones unlocked by carriers from USA and Europe, are having this issue after the unlocking process. Some people can solve it after a single restore, some other need more than 8 restores, and some of us have not solved it yet.
So my conclusion is that this issue should be related to Apple servers, because the only thing in common that i could find between O2 and ATT, or Vodafone and Orange, or Verizon and Telekom, is APPLE ACTIVATION SERVER.
Carriers really have no more to do here, they only send the unlock request to Apple and it is Apple which process it.
After a carrier send the unlocking request to apple there is nothing more they can do, everything else depends on Apple. So if Apple activation server is having issues with some IMEI or something like that, we will never know. Because Negligent persons at Apple are too lazy to take a look at that, they dont even search in google.
So lets wait
Carriers did their part and sent a request to apple.
If apple do not receive the request, they think it is the carrier which never made the request.