This morning I purchased 250MB of data from AT&T ahead of the auto-renewal schedule because I had used it up two weeks back. I then checked a few emails without downloading attachments and rode to work. Didn't use the iPad at work, though it would have WiFi there anyway.
About 2 hours after the purchase I receive the usual "only 20% of data left" email and am astounded by that, but go to lunch anyway. When I return from work I have the 10%, 2% and no data left email in my inbox.
I have iCloud Documents (though I only have a few of them), FaceTime and Reading List activated over cellular, but not iTunes. The iPad had been synced the night before, I was not signed in to Skype or similar and I actually didn't use it.
Anybody an idea what might have caused this??
I talked to the AT&T help line and all he was able to see is that the data was consumed in 5-6 bursts, not tickling over the three hours. But which service, no idea. I'll visit an Apple Store and check with them, maybe they have means to determine what went awry.