I just received a Motorola Razr v3xx I ordered. I powered it up and it worked fine. The seller said it was locked so I requested an unlock code from AT&T. I got it and when I inserted a non AT&T card to enter the code the phone froze on the "enter subsidy code" screen. It shut down and I haven't been able to turn it back on. I've tried charging it and swapping batteries but it still shows no signs of life. The only time it ever does anything is when the charging light turns on when I plug it into my computer without a sim card inserted. Why did this happen and is there any way to fix it?