NEW YORK, June 15 (UPI) -- Three of the largest U.S. Internet service providers are threatening to restrict their most active subscribers' online activity, companies say.

Time Warner (NYSE:TWX) Cable, Comcast and AT&T are considering charging those who use their services more than the average user, The New York Times (NYSE:NYT) reported Sunday.

Time Warner began an "Internet metering" trial this month in Beaumont, Texas, asking customers to select a monthly plan and pay surcharges when they exceed their bandwidth limit.

For its part, Comcast said it may slow down the connections of the heaviest users, so-called bandwidth hogs.

The newspaper reported AT&T said limits on heavy use were inevitable and that it was considering pricing based on use.

"Based on current trends, total bandwidth in the AT&T network will increase by four times over the next three years," the company said in a statement.

"Average customers are way below the caps," said Kevin Leddy, executive vice president for advanced technology at Time Warner Cable. (NYSE:TWC) "These caps give them years' worth of growth before they'd ever pay any surcharges."