[疑難求助] My Iphone line problem, pls help ， 描述： Iphone 4s

leo_83

Model: Iphone 4S (64Gb)
IOS: 5.1.1
I have a problem with my line, when there is no 3G, then my network line will go off and on, off and on~
I've tried restart, but it seems to have the same situation as long as there is no 3G, i cant even make call~
I've verify with other hp (Basic), the line is fine (With E /O) and can make call, but my iphone, once no 3G, no line...

Pls help~

Thanks~