It was working with your T-mobile SIM? Make sure you didn't upgrade to the 1.1 firmware or you might have bricked the phone part of it, however I have read that you can go back to the 1.02 firmware but am not sure if you can still use the phone, 1st check your firmware
i just did a restore. not update. it is at 1.0.2 right now. i just did a restore cause it was crashing on me. i just want to know how come after i did the system restore the t mobile sim card don't work on my iPhone?
Yes i had to do a restore to use anySim, wouldn't restore unless i allowed iTunes to download and install the latest firmware. If you were asked that and went ahead unknowingly there is a safe bet that it loaded that firmware on the phone. The method being reffered to above gives you the option to choose what firmware you want from a destination on your computer containing firmware 1.0.2. Did you check your firmware?
The only other thing I could think is that the phone was restored to in box condition meaning only AT&T would work. Check to see if AT&T Sim get an error message and then at least youll know if its all sims or just foreign.