I got a e709c from China. It worked in Taiwan. I carried it to USA. It does not work when I inserted my AT&T

I got a e709c from China. It worked in Taiwan. I carried it to USA. It does not work when I inserted my AT&T?
sim card. I went to the AT&T office. it can work inside the AT&T office without doing anything. But it will not work whenever I step out of the AT&T office. Can anyone tell me what may be the problem ? thanks!
PDAs & Handhelds - 1 Answers
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