I have 2 iphone 5's and 2 iphone 4's. One of the the 5's has the exact same problem. It uses data, all the time, even when she is connected to home wifi. I upgraded my plan, but we still go over. This has been ongoing for 18 months. We have spent hours on the phone with tech support, and hours in the apple store. No one can fix the problem. Every month AT&T credits the overage, but it is annoying to have to call every month. The last rep tried to tell me were eligable for an upgrade, and that a new phone may work better. I agree but not willing to spend all that $$$ and no guarantee.
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