NEED HELP with S2 on AT&T. I bought an unlocked version of the phone from Korea. Brought it to the US and used the AT&T sim with a $10 data plan meant for non-smartphones. Phone ran fine for 2-3 months. Data was a bit slow but worked and so did voice. The korean characters were bothering me, so I used ODIN to flash english version of the firmware (I9100). Ever since I did that, the korean characters are gone but voice and data are not functioning properly. Voice and data both only work intermittently. I tried the AT&T APN settings provided above but didn't help. Called AT&T and they seem to the think that the data plan needs to be changed to a Smartphone plan. I am willing to do that, but that shouldn't matter for voice right ? Can you please help. I don't want to go out and buy a new phone altogether.