I am still on an "unlimited" data plan and never paid much attention to how much data I use though it had usually been around 150 MB/month. So when it was time to convert my wife to an iPhone 4 from a BlackBerry, it seemed to make sense to only get the 200MB data plan - she was averaging at under 10 MB of data usage on her BlackBerry. Well, she ran ran over by 12MB the first month - in 3 weeks. In the first 6 days of the new (current) billing cycle she had already used over 40 MB. I felt that was a bit much, especially since she uses the device to text message, check email and phone - nothing else. I figured email is the culprit, viewing PDFs (new freedom, yay) etc. I checked her usage one morning and saw that she had just used 25 MB in an hour while at home and on WiFi!!! Email would be going over WiFi. I checked and she had not sent anything nor received/viewed large emails. I was able to rule out email. I then turned my focus to iMessage. Maybe iMessage is sending huge amounts of data versus SMS? So I disabled iMessage. This was also not the cause. All I know that on the AT&T website, the data usage is always SENT from the phone. I then compared her phone calls to those data usage charges and guess what? Each time my wife completed a call, there was a subsequent data transaction SENT from the phone. It is always at least 6 KB, but on occasion several MB!!!!! Is this normal? I have never heard of such a thing. I also compared my calls and it is true for me as well. (I have an iPhone 4S.) Give you an example: Yesterday I called someone as a test. The call duration was 7 seconds. And my phone SENT 764 KBs. Day before I called my wife at 6:34, we talked for 9 minutes, immediately after my phone SENT 276 KBs. 45 minutes before that I called my wife and hit her voice mail and hung up. Call duration was 3 seconds. Immediately after my phone sent 314 KBs. I could go on and on. All the above data is from the recent usage page on AT&T's site and almost all instances (except when I was actually using data, i.e. browsing, email) of data being SENT happen after a phone call completes. Due to the whole battery fiasco I have been paying a lot of attention as to what apps are running. I close my apps and then also remove/close them via the fast app switcher. I called AT&T and the first rep (who refused to give me his full name after I called his BS) told me that one should always turn off one's smart phone once a day for at least a minute as the connection degrades after a while, leading to dropped calls etc. I never heard that in my life, but he assured me he's been telling customers this for 14 years!! He also pointed out that one should turn off cellular data when around wifi networks. I asked him if this is in writing anywhere or what he is basing these "suggestions/resolutions" on. He had none. I asked him for his name, he wouldn't give it and so I asked for a manager. I was transferred but again, received the advice to turn of cellular data if I want to avoid data charges. I made it clear to the person that I do expect to be using data, I just don't know why it would coincide with every single phone call my wife makes (and I for that matter). Why would I need to click 4 times to turn of cellular data if this is sooooo recommended??!?!?!?!?! Wouldn't it be more accessible? Or why wouldn't the phone do so automatically? Anyway, I am obviously not satisfied with those suggestions. In fact, it is scary. Imagine others going over their 200 MB plan because of this? I think this might be an iOS5 thing but not sure. I just can't see a random app doing this. Any ideas? Have you checked your AT&T data usage and compared it to your calls? I can provide more data if needed.