Thursday i had used 480mb with 6 days left of my Iphone 4vodafone allowance (1gb).
Amazingly in 6 hours i lost nearly 400mb - where the hell did it go? I closed all applications on my Iphone 4 so i don't understand - maybe i did not close an app down properly (I sometimes check and close them using double tapping and deleting from the tray).
Happen to anyone else? convinced you had exited the apps but still found data being used heavily?
I did install the Metro (newspaper app) but that was after the leaking started.

Metro seems to use very little, I have that one with push notifications on, and yesterday I only used 13mb.

Sounds like an error, chewing through that much data in such a little time seems fairly difficult, unless something was streaming (which you would surely have noticed?!)

Just got the idatausage app to warn me next time - strange one this is as nothing was streaming at the time.