AT&T 3G data plans for iPad
Data per month Price per month
250MB/month $14.99
Unlimited $29.99
Can I use my current iPhone service plan with the iPad?
No. The cellular plan for iPhone is separate from the iPad plan.
FROM. http://store.apple.com/us/browse/home/shop_ipad/family/ipad?mco=OTY2ODA0NQ