My wife has an iPhone 4 on our family plan.  She has a 200 MB plan which she's about to exceed for this month.  I'm looking at her data use and trying to figure out where the 200 MB is going.

I notice that every night around 12:30 AM there's data use showing of about 4 MB.  That's around 120 MB in a 30 day month and I have no clue what it's for.  At that time of night the iPhone is charging, locked, and a few feet away from our wifi access point.

Might anyone have a guess that can be happing at that time every night that's being charged to our data plan, especially since the iPhone is connected to the Net via wifi?

Thanks in advance for any light you can shed.