AT&T is charging me for data when my cellular data is off?

At&t has charged me for data I did not use. First Id like to say that I have the iphone 4s and it allows me to turn of the cellular data. I keep my phone on Wi-Fi most all of the time and always keep the cellular data off. My phone shows me how much data I have used too and It still says I have only used 553mb of data usage. My problem is I went to sleep and my cellular data was turned off. I wake up in the morning with 2 new texts saying that I have used all of my data, and on top of that I had another text that said for twenty dollars we can give you more data. Heres the kicker, they charged me the twenty dollars to add more usage all while I was asleep! Can anyone please make sense of this? I contacted at&t and they were no help insisting that I had used this data. Like I said my data still says I have only used 553mb. Before anyone says someone may have grabbed the phone and been using it, Its not a possibility.

You'd be surprised at all the data that your phone uses without you realizing it because of your settings alone. Do you have GPS tracking on? There's data usage right there. Location services take up a lot of data, especially if you're moving around. Your phone should be able to tell you what applications use up the most data. And actually, ATT should be able to tell you what applications are accusing the most space in your phone. You should be able to call them and ask them and they should be able to tell you.

If you went from a 3G to a 4G device then there's a good chance that more data will be used. This is because on 4G, the data travels faster, allowing the user to do more in less time. Also you should check your Fetch Data settings if you have any on your phone. You can burn up to an extra three gigs a month by just having those set wrong. Just by changing your fetch data to every hour as opposed to every 15 minutes, you can probably save a lot of data usage. Hope this helps.