The carrier hasn't provided more precise estimates for any customer shift, although its strategy is less dependent on "any one device," according to company officials. AT&T has said that its agreement to subsidize the price of the iPhone 3G will have an effect on its near-term income but is counting on long-term revenue from contracts to make up the difference.

Verizon also asserts that the original iPhone onwards have had a stimulating effect on its own sales. Over 30 percent of phones sold are now smartphones, the firm says. These devices often have a higher up-front price and are similarly more lucrative in the long term, as customers are more likely to attach data plans and other services that translate to a higher average revenue per month for each user.

The claims follow data from a spring quarter in which Verizon says it added 1.5 million net customers, outpacing AT&T's 1.3 million during the same period and narrowing AT&T's lead in its total subscriber base. AT&T however dealt with iPhone shortages during that quarter that it says affected its results.