I am using iPhone 3gs, it was jailbroken before and was working pretty good.
But I called to ATT with official unlocking request and they unlocked it for me. They sent some email with unlocking instructions (that is backup and restore via iTunes).
I followed instructions but during this also was upgraded to iOS 5.1.1.
Now it says that cannot connect to activation server and suggests to activate via iTunes. But iTunes says "There is no SIM card installed in the iPhone you are attempting to activate". On phone screen it shows as "No Service"

Any help pls ? what I'm doing wrong?