When I bought my iPhone 3G I gave my brother my original iPhone. He'd like to use it with a very basic all-voice (not data) AT&T plan, but they told him that even if his plan lacks data, the iPhone will still connect the AT&T's EDGE network and he will get charged ridiculous amount by the KB. Is that true? Is there any way to prevent the iPhone from using AT&T's data network for ANYTHING, but still have it capable of making voice calls and using WiFi networks? Thanks!