Today I got my Sprint iPhone 4S. Of course I had to settle the unlocked-locked-unlocked Sprint debacle. I popped in a good AT&T micro-SIM card from a colleague.
Then I rebooted… I managed to make it into Settings > General > About > Carrier and briefly saw AT&T. Then my phone rebooted into the Activation Screen.
When I tried to activate I got the following disappointing message:
Only compatible SIM cards from a supported carrier may be used to activate iPhone. Please insert the SIM card that came with your iPhone or visit a supported carrier’s store to receive a replacement SIM card.
Did anyone have different luck?