AT&T is the exclusive U.S. carrier for the Apple iPhone as well as a plethora of other smartphones and mobile devices, and it’s no secret that the company has had difficulty expanding the capacity of its wireless network to keep up with the bandwidth demands of all those mobile users. The company has been aggressively building out its network to increase capacity, but now it appears the company is considering other ways to get its mobile users under control: changing service plans so high-bandwidth pay more to push so much data through the network.

Speaking at a UBS investors conference in New York, AT&T’s head of consumer services Ralph de la Vega said the company is considering ways to get high-bandwidth users to “reduce or modify their usage” in order to free up bandwidth for other users. De la Vega did not offer any specifics, but AT&T is widely considered to be eye usage-based fees for mobile broadband data, rather than the flat rate all-you-can-eat data services it currently offers.

According to De la Vega, about three percent of smartphone users are consuming about 40 percent of AT&T’s network capacity, with video and audio streaming consuming being responsible for a good deal of that bandwidth consumption. De la Vega also reiterated AT&T’s claims that it offers the fastest 3G service in the United States, and contended most problems with data congestion occur in the San Francisco and New York City areas. The company is working to build out its network capacity in those markets and others. De la Vega also said the company is working on tools to help mobile users better monitor their data utilization.

Changing over to a usage-based fee system for mobile data could be a major headache for both AT&T and its customers, most of whom don’t want to be bothered with having to meter data usage in the same way many mobile phone users monitor usage minutes: one reason flat-rate plans are so popular is that they eliminate headaches and guesswork involved in mobile communication. However, if AT&T really is trying to reign in just the top 3 percent of smartphone users, it might be able to introduce a usage-based plan as a cost savings to ordinary phone users…and that might just earn the company some points in consumers’ eyes.