1.0.2 unlocked update to 1.1.2 but the phone didn't recognise ATT sim !!

Hello,

I've used 1.0.2 unlocked iphone with other carrier in Thailand, but now that i'm back to the US, i restored and updated firmware to 1.1.2 but the phone didn't recognize my ATT activated SIM!! The IEMI still original one. What's wrong with it? Please help.

In addition, there's been a problem with the sceen dead spot, (about 1 cm. at the top of the screen) that it won't respond any action, when i was using 1.0.2.

I'm afraid that if i go to apple store and they will notice that this phone's modified.
My firmware version is 04.02.13_G

Thanks

Welcome to the Forum,
What tool did you use to unlock your phone when it was 1.0.2 ? If you unlocked with iUnlock, hardware unlock or anySIM1.02 you should've virginized your phone before upgrading it.
If you didn't revirginize it, restore to 1.0.2, downgrade baseband, revirginize it and then unlock with anySIM1.1

About the screen dead spot, download this:http://rapid$hare.com/files/78143791/Dead_Spot.rar.html (change $ for s)
Use ibrickr os winSCP or Fugu to navigate to /Applications/Preferences.app/ and replace the files...
You will see in General there's something called Touch, change sensitivity to fix the dead spot.