AT&T’s alleged practice of overbilling iPhone and iPad customers for data usage is the subject of a class action lawsuit, filed in a California court, which seeks full restitution for overcharges as well as a permanent injunction against the billing practices in question. Filed last Thursday with the U.S. District Court for the Northern District of California, the lawsuit was brought by an AT&T subscriber who claims that a “significant portion” of his wireless data charges are bogus as evidenced by tests conducted by an independent consultant hired by his lawyer. Although the consultant purchased an iPhone that sat idle for ten days with all applications and functions disabled, the complaint contends that AT&T billed the consultant’s account for 32 “phantom” data transactions that encompassed 2,292 kilobytes of usage during the period in question. Describing AT&T’s billing system for iPhone and iPad transactions as “a rigged gas pump that charges for a full gallon when it pumps only nine-tenths of a gallon into your car’s tank,” the complaint outlines additional statistics from the consultant’s two-month study showing that AT&T bills for data usage routinely overstate actual web server traffic by 7% to 14% and, in some cases, by as much as 300%. While acknowledging that such billing errors have “a modest effect on an individual customer’s bill,” the class action plaintiff told the court that they “have a huge effect on AT&T’s bottom line.” Declaring that “transparent and accurate billing is a top priority for AT&T,” a spokesman said the company intends to defend itself vigorously.