• by Wendy Davis , Staff Writer @wendyndavis, May 6, 2015

Facing pressure from regulators, AT&T said today that it will revise its practice of throttling some smartphone users who subscribe to old, unlimited data plans.

Now, instead of automatically throttling unlimited customers after they exceed a monthly allotment, the company only slows down those users when the network is congested.

“Customers on an unlimited legacy data plan may experience reduced speeds only when using data services at times when in an area where the network is experiencing congestion,” a company spokesperson confirmed today in an email to MediaPost. The company quietly changed its policy within the last five weeks, according to Droid Life, which first reported on the revision.

The move comes several months after the Federal Trade Commission sued AT&T for allegedly duping consumers by offering them “unlimited” data plans only to throttle them for exceeding a monthly cap.

The carrier began throttling users in 2011, soon after it introduced “tiered” billing plans, which require people to pay for monthly allotment of data. The wireless provider still allows longtime users who previously subscribed to unlimited plans to keep them, but throttles those customers after they hit a cap of either 3GB a month (for the 3G and HSPA+ networks) or 5 GB (4G LTE network). People on the 3 GB network were only throttled when the network was congested, but all users of the 4G LTE network who exceeded the cap were throttled automatically, according to Droid Life.

Since 2011, AT&T has throttled more than 3.5 million customers, the FTC alleged in its complaint.

The FTC isn't the only agency to express concern about throttling. The Federal Communications Commission also has criticized the carriers for slowing down users -- and now that the FCC has reclassified Web access as a utility service, the agency is in a position to exert more oversight over mobile broadband.

At first glance, AT&T's new policy, while preferable to its former one, doesn't seem likely to satisfy the FCC.

That's because the new policy continues to treat legacy customers with “unlimited” data differently from those who pay per byte.

FCC Chairman Tom Wheeler made clear last year that this type of discrimination raises concerns.

He weighed in on the subject soon after Verizon announced that it intended to start throttling some of its “unlimited” subscribers. That company's plan called for it to slow down some users of the 4G LTE network during times of heavy congestion. Verizon said it would only apply that policy to people who consumed more data than 95% of other subscribers.

Wheeler was among the first people to pan that proposal. “I know of no past Commission statement that would treat as 'reasonable network management' a decision to slow traffic to a user who has paid, after all, for 'unlimited' service,” he wrote to Verizon last year.

The company retreated in October, when it announced it wouldn't move forward with the initiative.