The Federal Trade Commission filed a federal court complaint against AT&T Mobility, charging that the company has misled millions of its smartphone customers by charging them for “unlimited” data plans while reducing their data speeds, in some cases by nearly 90 percent.

AT&T called the FTC’s allegations baseless. Operator further adds that it’s baffling as to why the FTC would choose to take this action against a company that, like all major wireless providers, manages its network resources to provide the best possible service to all customers, and does it in a way that is fully transparent and consistent with the law and our contracts.

“We have been completely transparent with customers since the very beginning. We informed all unlimited data-plan customers via bill notices and a national press release that resulted in nearly 2,000 news stories, well before the program was implemented.  In addition, this program has affected only about 3% of our customers, and before any customer is affected, they are also notified by text message,” said Wayne Watts, Senior Executive Vice President and General Counsel, AT&T.

The FTC’s complaint alleges that the company failed to adequately disclose to its customers on unlimited data plans that, if they reach a certain amount of data use in a given billing cycle, AT&T reduces – or “throttles” – their data speeds to the point that many common mobile phone applications – like web browsing, GPS navigation and watching streaming video –  become difficult or nearly impossible to use.

The FTC alleges that AT&T, despite its unequivocal promises of unlimited data, began throttling data speeds in 2011 for its unlimited data plan customers after they used as little as 2 gigabytes of data in a billing period. According to the complaint, the throttling program has been severe, often resulting in speed reductions of 80 to 90 percent for affected users. Thus far, according to the FTC, AT&T has throttled at least 3.5 million unique customers a total of more than 25 million times.

Earlier, AT&T had announced that starting October 1, 2011, smartphone customers with unlimited data plans may experience reduced speeds once their usage in a billing cycle reaches the level that puts them among the top 5 percent of heaviest data users.

The complaint charges that AT&T violated the FTC Act by changing the terms of customers’ unlimited data plans while those customers were still under contract, and by failing to adequately disclose the nature of the throttling program to consumers who renewed their unlimited data plans.

In 2012, operator has clarified that for customers with a 4G LTE smartphone – who also still have our unlimited data plan – data speeds will be reduced if usage is 5GB (gigabytes) or more in a billing cycle. Speeds will return to normal at the start of the next billing cycle.