We made numerous calls trying to solve the dispute with those reps, but failed. When we asked to talk to supervisors/managers,the reps declined to transfer and only said the supervisors would call back. Unfortunately none of the times we got any response. They kept overcharging their customers. We cancelled the service and will pay the cancellation fee. But we will let other people know that and stay away from AT&T.
We post this on the local chinese email list, see the responses we got. Of course the service may varies from place to place!