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Things like push notifications, apps in the background that require an internet connection refreshing constantly, and using apps that require internet connection :)p) will all go toward your data usage. I highly doubt that AT&T is 'sticking' it to you and that you simply just lost track of your usage.
 
I'm NOT upgrading.
Than the issue is your own fault
I too started with the unlimited plan, but downgraded because I was rarely using 150mb, but as soon as I scaled back along came the increasing in data used.

I'm guessing that move pissed AT&T off and now they're sticking it to me.

Be forewarned.

Nope, pretty sure they're sticking it me. At least when the throttling-backs begins this fall, I'll be use to AT&T d!@king me over.

I doubt AT&T cares about one customer changing their dataplan.
 
Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_5 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8L1 Safari/6533.18.5)

AT&T has a "known issue" as they called it. It's a billing issue and they will credit you back the overage. It took me five customer service reps and two stores, but I found someone who had seen it recently. Mine started this billing period. Four days into my billing cycle I used three times my typical monthly usage. They acknowledged the problem and said they are trying to fix it. Until they do just ask for a credit on the overage and they will issue it.
 
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