the three-year anniversary for the iPhone

Expectations that AT&T will lower the cost of wireless service for Apple's iPhone are growing. A $20-a-month data plan with limited access is a possibility for the exclusive U.S. iPhone service provider.

AT&T's monthly plan for the iPhone is currently $69 plus taxes and fees and includes a $30 unlimited data plan. A comScore study found that 43 percent of current iPhone users have incomes above $100,000, so AT&T needs a lower price for it and Apple to grab a larger share of the smartphone market.