All of the major U.S. wireless carriers announced unlimited calling plans in February, but apparently AT&T's wasn't applicable to the Apple iPhone. IntoMobile discovered that AT&T just updated their iPhone pricing plans to include an unlimited voice plan for iPhone owners. The unlimited plan is US$119.99 and includes unlimited voice minutes and unlimited data (a default for iPhone service). BlackBerry and PDA plans with data and unlimited voice start at US$149.99 per month.
However, this plan still only includes 200 text messages so you will have to pay for additional text messaging coverage. The table of plans (on the Apple site) also has Rollover Minutes checked, but I have no idea how you can rollover unlimited minutes. A reader pointed me to the correct AT&T site that shows the updated table of features for this unlimited plan (click on the Plans tab).
I guess you would then get infinity voice minutes with AT&T.