First, a little back history. In June AT&T introduced new tiered data plans for its customers. That included a DataPlus plan that provides 200MB of data for $15 per month and a second DataPro plan that costs $25 per month and provides 2GB of data.
As of that day in June, AT&T's "unlimited" data plans were no longer available. New AT&T customers now have to choose between the two capped plans, and if they choose the 2GB DataPro plan, each additional gigabyte per month over that allotment costs $10. However, as the Associated Press pointed out today, there's a loophole.
I just contacted AT&T Customer Support and asked about adding the unlimited option back to my account. Since June, I've had a 2GB data plan (it made sense when I wasn't using a ton of data), but I now have an iPhone 4 and would like more data. I was told that this is possible, since I once had an iPhone with an unlimited account, and that I'll be able to be "grandfathered in" to the unlimited plan again.
So there you have it. It appears there actually is a loophole for getting more data each month. AT&T customers that have been around a while may want to give it a whirl for themselves.