You can probably terminate the contract for a fee...according to the site below $175.
http://www.theregister.co.uk/2007/06/26/iphone_contract_prices/comments/#c_26955
Some other tidbits:
"ATT (Cingular) customers pay only $20/month to add an
iPhone = $1000/2 years (about half what this story quotes).
http://www.apple.com/iphone/easysetup/rateplans.html
on left it states:
"If you’re already an AT&T customer and want to keep your current voice plan, you can just add an iPhone Data Plan with unlimited data (email and web) and Visual Voicemail for just $20 per month."
Who can do better for unlimited WIFI & ATT web access anywhere plus phone and iPod for $20/mo anywhere in the world?
======= other links to $20 fee to ATT customers ===========
http://www.slashgear.com/att-unveils-new-wireless-plans-for-the-iphone-265921.php
http://www.rcrnews.com/apps/pbcs.dll/article?AID=/20070626/FREE/70626004/-1/allnews
http://www.apple.com/iphone/easysetup/rateplans.html"