AT&T said that it will slow data speeds for those exceeding certain data limits. (RICK WILKING/REUTERS)

AT&T clarified its data policies Thursday, saying it will slow data speeds for users who exceed either a monthly limit of 3GB of smartphone data or 5GB of data on the carrier’s 4G LTE network.

The company, which switched to tiered data plans for new users in June 2010, had previously said that it would slow data speeds for the top 5 percent of data users who had been allowed to keep their older, unlimited plans. Legacy customers with unlimited plans pay $30 per month, the same as users who buy a data plan with a 3GB cap.

But unlimited plan customers complained that, in some cases, their speeds were being limited after using around 2GB data and they were being forced to pay the same price for less data than tired plan customers. Thursday’s changes were seen as a reaction to those complaints.

“Our unlimited plan customers have told us they want more clarity around how the program works and what they can expect,” said AT&T spokesman Mark Siegel in a statement. Siegel said that the plan will still affect about 5 percent of AT&T’s customers, and that users will be notified if they approach the data limits via text message.

Last week, a Simi Calley, Calif. judge ruled that AT&T should pay iPhone user Matt Spaccarelli $850 in a small claims court. Spaccarelli said that AT&T’s his bill showed he had used between 1.5 and 2 GB of data before his data speeds were reduced, and questioned the motive behind the throttling policy. According to a report from the Associated Press, other AT&T users using similar amounts of data were told their speeds were being limited because they were among the top 5 percent of data users in their region.

Matt Wood, an analyst at the media reform advocacy group Free Press, said that while he wouldn’t call AT&T’s new policy good news, the plan seems to provide “some sort of parity” between tiered plans and the older, uncapped plans.

“The picture is in shades of gray,” he said. “This might affect more users, but it might be more fair.”

He added said that slowing data speeds is not necessarily a bad thing, but called it a “blunt tool” for wireless companies looking to ease traffic congestion.

In fact, a recent study from the wireless analysis firm Validas found that those on tiered plans and unlimited plans generally use the same amount of data. On the Verizon network, the study found that those on tiered plans actually used more data than those on unlimited plans.

AT&T, fresh off its failed bid to acquire T-Mobile and boost its spectrum portfolio, has been struggling with ways to manage its network congestion. The company recently raised rates for new data plans on smartphones and tablets by $5, citing increased data use across its network as the reason for the change. The company also cited increased data traffic as a driving reason behind its decision to throttle data for unlimited users.

“Because spectrum is limited and data usage continues to soar, we manage our network this way to be as fair as possible,” Siegel said.

Related stories:

AT&T increases data plans for smartphones, tablets

How AT&T fumbled its $39 billion bid for T-Mobile