AT&T offers business plans for the iPhone
Some basics of the business plans are the same as the personal plans. In order to sign-up as a business user you will need to activate a two-year or renew an existing two-year contract if you are already a customer.
There are three levels of business plans available: Enterprise Data Plan for iPhone 200; Enterprise Data Plan for iPhone 1500 ; Enterprise Data Plan for iPhone Unlimited. The business plans all come with unlimited domestic data and visual voicemail.
There are also two global add-ons for business users, allowing you to travel to 29 other countries and still receive data. The first plan gives you 20MB of data and costs $24.99; the second plan costs $59.99 and gives you 50MB of data.