just lost my iphone, it never been unlock or jailbreak. Did some reading about IMEI numbers on a phone. It says if I call ATT they can block my phone's IMEI number so the phone can not be use again. Now my question is, if that lucky someone unlock my phone, can it be use on ATT or Tmobile?????

... looks so, as you can "spoof IMEI for discount purposes"...

I'm sad for you pal.

If that someone unlock my iphone and use it on ATT or Tmobile, can ATT still track my phone using the IMEI number?? then find out which sim card the phone is using, then i can get the phone back.