I have a very similar problem. I have a Samsung S3, not rooted, but unlocked from Verizon. I have been in Kandahar for a month or so. My SGS3 with a local provider will make and receive calls great when coverage is there. My problem is, I can only seem to text local here not back to the US, or get email and no Google Talk. I went to the shop where I got my card here, they told me that Verizon needed to unlock my phone. I know it is unlocked but I made the call home, Verizon told me what I already knew. I went back into the store, once again, next they said Verizon needed to unlock my APN? I called again, finally I got a response from Verizon saying that Samsung needs to release the patch so Verizon can unlock it. If anyone knows of such a APN patch I would greatly appreciate it. My lap top screen got cracked during a patrol so doing all of this and email is quite the B!tch! I have always had success with this forum and hope it will continue. Once I send my lap top back home to be warrantied, I will not have any way of getting the usual business done for at least a month. I'm trying to hold off on the lap top until I can get my phone fully functional. I do not have internet connection on my phone, just my computer, I guess that is the APN, that is still locked. I could do all of this if I had WiFi, but it is not allowed here by the company that provides internet. They do have WiFi in some areas, but it is always bogged down with everyone else trying to use it. Also, I am not too sure if I want to attempt to do a root, the internet service here is very slow. Thanks for your help. Please remember, I am atleast 8 1/2 hours ahead of you, so response time will be delayed.
A very helpful member of GalaxyS3forums sent me here.