Why is my iPhone using so much data

My Wife and I have the 200MB plan because we rarely use 3g data. The wife is 90% of time around home Wi-Fi, but for some reason her bill will be 200-400mb above our cap with a hand full of 50-100mb data transfers. I called ATT and they can't tell me exactly what app/ service is doing this xfer, simply that it happened. So long story short, I was wondering if there's a way to audit the iPhone to find out why this 3g data was being used when she physically wasn't punching away at the screen

Check if your 3G is enabled or not. On your iphone, go to Settings - Network- and if your 3G is enabled, make sure to turn it off. Hope this works!

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