AT&T offers : one for $14.99 for 250MB, and the other for $25 for 2GB, whether purchased prepaid or post-paid.

AT&T is sweetening the deal by offering the first month free to customers who activate a new post-paid account at $25 for 2GB.

Also, the Personal Hotspot feature that is a part of iOS 4.3 will be available to AT&T customers who pick a $25 plan for 2GB, plus the $20 per month for a tethering option that provides an extra 2GB. That would be a total of $45 for 4GB monthly.

If you pay in advance at AT&T with a credit card, overage charges are the same as buying a second plan for 250MB for $14.99, or 2GB for $25.

If you pay after exceeding your data plan limits (on your AT&T phone bill), the overage for the smallest plan is an additional $14.99 for another 250MB, but only $10 per 1GB of overage on the 2GB plan.