On Friday, Verizon announced that it was reducing the cost of its unlimited calls plan, and AT&T quickly responded with similar discounts. Thus, you can now get an unlimited voice and data plan for the iPhone for $100, which is $30 cheaper than it was before Friday. If you have a Family Talk plan, you can have unlimited voice and data on two iPhones for $180 a month.
From what I am reading, you can go online to www.att.com/wireless and change your current plan to take advantage of the lower prices without any penalty or contract extension. If you have success doing so, I'd love to hear about it. I don't use an unlimited plan myself; while the Phone feature of the iPhone is essential for me, my wife and I rarely use more than a few hundred minutes a month so we have the smallest Family Talk plan.
If you don't need unlimited voice calls, the other monthly choices for iPhone users (including unlimited data) are 900 minutes for $90 or 450 minutes for $70. If you have a Family Talk plan with two iPhones, your choices are 2100 minutes for $170, 1400 minutes for $150, 700 minutes for $130, or 550 minutes for $120.
For all of these plans, you still need to pay extra for text messages, and that price remains $20 a month for unlimited texts ($30 for two phones on a family plan). Cheaper text plans are 1500 texts for $15, 200 texts for $5, or pay-as-you-go texts for no monthly fee and a charge of $0.20 per Text/Instant Message and $0.30 per Picture/Video Message.