so I have gotten the att device only factory unlocked, which work fine with tmobile usa, and other carriers until 2 days ago! First I got invalid sim thought it was the sim. So I went to the store and replaced it nada happened still same issue. Restore the phone to the latest firmware got a bit better with carrier reception, but cannot call or text! now I have tried restoring 3 times with 3 different carrier sim card, which I get receptions but cannot make call or text. Anybody having this type of issue? I think its a damn defective iphone which I will have to swap once I get back to the states. Man this is really frustrating. I never had any issue before with any iphones that I have owned especially a brand new iphone.