The company is making a few changes to its monthly plan, boosting rates and adding a separate charge for text messages.
Users will pay an extra $US10 for the upgrade from a slower Edge connection to the 3G network.
Prices will range from a US$69.99 monthly plan with 450 anytime minutes and 5,000 night and weekend minutes, to a US$129 plan with unlimited minutes. Each of the plans will include unlimited data transfers.
SMS will be separate, with prices ranging from US$5 per month for 200 messages to US$20 per month for unlimited messages.
AT&T also revealed a new pricing plan for the handsets. Customers signing a two-year contract can pick up the iPhone 3G for US$199 (8GB) or US$299 (16GB).
Customers not deemed eligible for an upgrade will have to pay US$399 and US$499 respectively for the iPhone 3G.
"We cannot wait to offer the iPhone 3G to our customers, and we want to make sure that the buying process is as easy as possible," said Ralph de la Vega, president and chief executive at AT&T's wireless unit.
"Considering all the great new features of the iPhone 3G, we think our pricing and monthly plans present a tremendous value for consumers and businesses alike."
AT&T said that it will also soon offer the iPhone without a contract for US$599 (8GB) and US$699 (16GB).
The handsets themselves will still be locked into the network, although the iPhone hacking community will no doubt be hard at work on another 'jailbreak' procedure.
Apple has long distanced itself from the efforts to remove the iPhone from its exclusive network.
The company has said that, while it does not deliberately cripple hacked iPhones, it will not be held responsible for the compatibility issues that often arise with firmware updates.
The iPhone 3G will go on sale on 11 July at 8.00am and will be available only at Apple and AT&T retail stores.
AT&T reveals iPhone 3G price plans
By Shaun Nichols on Jul 5, 2008 6:30AM