I have a Storm, unlocked and using AT&T 9530 with .75 OS (just downgraded from .148).
My problem is that today I went through the mountains and lost all signals. The signal strength on the screen just said "OFF". When I got back to an area covered, my Home screen had no AT&T sign. I tried to make a phone call, and got the operator from Verizon Wireless telling me that I needed to call VZW.
Anyways, I did BattPull and SimPull, rebooted and I was back up and running. I put the phone in it's holster until I got back home. Pulled it out to make a call and I'm getting the same operator. BattPull/SimPull = nothing.
I wiped and dowgraded phone and OS to see if that would do anything, nothing at all.
Under my Manage Connections, it says:
Turn All Connections Off
Mobile Network: Verizon Wireless (I have an AT&T sim in)