IPhone using extremely high amounts of data when not in use

Question

I have a 4S on AT&T and am grandfathered in w/ the unlimited data plan. Last month I got the notification that I was in the top 5% of data users (which sounds crazy to me considering what some other people I've read about seem to use). According to AT&T's site I had used 2.09 GB with 16 days left in my billing cycle.
Once I got that notification I logged on to see if I could find out when I was using such large amounts of data. It turns out between midnight and 1 am almost every night there was large amounts of data sent. I think this is strange since for two reasons, 1) I'm on WiFi at home in my apartment and 2) I wasn't even awake at the times these charges occurred.
Example: January 6, 2012 at 12:40 am I was charged for 417,327kb, roughly 417MB.
Similar data usage occurred almost every night going back to 12/28/11. On 12/29 I was charged for 468MB at 12:21am. Very unlikely this was actually data I used since I had work the next day and wasn't awake. It honestly looks like 80-85% of my data usage is coming from these occurrences. It also isn't likely that this is a total of data used throughout the day as there are other entries of smaller amounts spread out throughout the day.
Now, if I was on a truly unlimited plan and there was no such thing as throttling I really wouldn't care about this. But the fact is that my 3G speeds are being throttled (just ran speed test at a location I used to get over 1Mbps and I am was at .07 Mbps). I have spoken to AT&T and they insisted it was an issue w/ my phone, either the hardware or the OS. So I went to apple and the "Genius" did a DFU restore for me in store and told me that would fix it. It hasn't and now I'm stuck with this constantly happening and unbearably slow 3G data speeds for the rest of the month.
That was my last billing cycle where I was throttled down to download speeds of .07mbps. Unusable. This month I decided to closely monitor my data usage. I turned off iCloud and photostream, and turn off data whenever I'm using wifi. I turned off the sending info to apple setting.
I checked my account on ATT.com today and noticed that yesterday morning at 7:58 am while driving to work I somehow used 247 MB. Don't ask me how, I'm not steaming anything and my phone is either locked or playing music from the iPod app. I could probably stream Netflix for 5 hours and not use that much data.
I called AT&T to let them know (AGAIN) and got bumped up to a "Data manager" who was incredibly b*tchy and rude. She said there must be some app that's using that much data to update. I don't have any apps that are even that size so I don't see how this could possibly be the case. I tried to talk with her about how that can't really be the case and she just kept repeating that there must be some app using the data blah blah. I've gone to apple with this last month after failing with AT&T and at first they did a DFU restore and we restored the phone as new, then it kept happening so I went back they replaced my phone. AT&T said it must be a hardware or software issue last month, but this month it must be an app that's doing this. I can't get a straight answer from them and they just keep passing the ball to say it's Apple's problem.
I really don't know what to do. I'm grandfathered in on the unlimited plan and don't really want to change that. Say I change my plan to the 3GB's at the same $30/month. What's to say this won't keep happening and I'll be over that 3GB's in 10 days then get charged an extra $10 for each additional GB?!
I can't think of any apps I've downloaded in the past few months that would result in this change and I can't live with another 2/3 of my billing cycle being throttled down to unusable speeds.
Has anybody else had anything similar happen? I have no idea what to do next (and sorry for the long rant but I'm fresh off the phone with AT&T and I'm ******)

Answer 1

Thanks for the link. I only went through the last three pages and unfortunately it looks like there is no solution. I turn data off every night and turn it on only when I'm not in a wifi area. It seems that as soon as I turn it on, within an hour it charges me data for a backlog of whatever it didn't do when it was connected to wifi.
I think it's absolutely disgusting that AT&T can just dismiss this and act like it's the users fault. Apps and email updating in the middle of the night to the tune of 400MB? I highly doubt it and then when I called to ask them about it they try to make me sound stupid like I have an app or two open. Just really ticked me off. The worst part about it is that there doesn't appear to be anything I can do about it aside from never using my data.