How to activate 3Gs after iOS 6 update

I have a 3Gs, which I did jailbreak before. It is on iPad baseband. I did the SIM unlock also. It was AT&T locked before. And I lately upgraded it to iOS 6 without doing my homework before. After the update the screen says that it could not be activated. How can I solve this situation? By the way I did the SIM unlock through AT&T too, after this incident. Thanx for any help