By David Shepardson

WASHINGTON (Reuters) - Cable TV companies Time Warner Cable and Charter Communications Inc agreed to provide billing credits and make other changes after a U.S. Senate committee found overbilling to thousands of consumers.

Other cable firms said they are eliminating some fees and trying to make it easier to cancel service.

The Senate's Permanent Subcommittee on Investigations said in a report on Thursday that Time Warner Cable and Charter Communications Inc <CHTR.O> "have consistently failed to provide refunds to customers whom they knew they overcharged."

The companies made no effort to trace equipment overcharges unless consumers asked and did not provide notice or refunds, it said.

"Instead of correcting their mistake by refunding the overcharges, their practice has been to just pocket the money," said Senator Rob Portman, an Ohio Republican who chairs the panel.

Executives of Time Warner - which was acquired by Charter in May - told the Senate panel it will provide an automatic one-month credit to customers for overbilled equipment or service.

Charter said a company audit found overbilling in approximately 63,000 of 11 million boxes, or less than 1 percent. The company will give overbilled consumers a one-year credit and has implemented controls to prevent future overbilling.

Executives from Comcast Corp <CMCSA.O>, Charter, DirectTV - a unit of AT&T Inc <T.N> - and Dish Network Corp <DISH.O> testified before the panel and pledged to improve customer service. A former Time Warner Cable executive also testified.

Senators said cable bills are too complicated and questioned some fees to cancel service.

Comcast, the largest U.S. cable company, told the Senate panel it would make it easier for consumers to cancel service without being forced to stay on the phone and answer questions.

Comcast has launched a pilot project to allow consumers to request to cancel service online. It has recently eliminated change of service fees, extended the time to dispute fees and made it easier to dispute fees.

Senator Claire McCaskill, a Missouri Democrat, said the best rates for subscribers are never advertised. Customer service representatives are taught not to be honest with consumers about the best price unless the customer is angry and threatens to cancel, she said.

"Nobody knows how to get the best price from you," McCaskill told the executives.

A recent American Customer Satisfaction Index survey found pay television service ranked near the bottom of the 43 industries surveyed.

The Federal Communications Commission has proposed allowing consumers to swap pricey cable and other pay TV boxes for cheaper devices and apps, a change that would boost competition in the $20 billion television set-top box market.

(Reporting by David Shepardson; Editing by Dan Grebler)