quick to bill, slow to queries

A month ago I realized something wasn't right with the bill I recieved for my iPad. I phoned in and the lady confirmed that something didn't match up on my invoice and itemized billing. She logged a billing query and said they would get back to me. ***. I have heard nothing and now have the same query on my new bill. I phoned in and they said they needed me to give more information. So I asked how I should know that was the feedback and they said they smashed me . . . . On my iPad!!!!!! Now their systems are down so I still have no answers and you are taking money I don't believe is yours and that I can't afford to wait a month to get back. I'm irritated and would appreciate some feedback.