(Bloomberg) -- Viacom Inc. is warning pay-TV customers of AT&T Inc. that they could lose access to channels such as Nickelodeon and MTV unless the companies reach a new programming agreement.

The current contract between the parties expires Friday, Viacom said Tuesday in an email. The media company began activating a “crawl” message on its networks, alerting customers of the looming dispute. The owner of DirecTV, AT&T is the largest pay-TV provider in the U.S., with 24.5 million subscribers.

Viacom, which also owns Comedy Central and BET, says it has made a series of offers to AT&T that allow the company to lower customers’ bills. The New York-based media company accused AT&T of using its new market position, as owner of Time Warner, to favor its own content.

Price disputes between media companies and pay-TV system owners reflect pressure on both sides to squeeze more money from a shrinking pool of cable and satellite customers. Programmers like Viacom count on ad revenue and subscriber fees to pay for the TV shows and movies they air. Pay-TV system owners like AT&T are losing customers to lower-priced options like Netflix Inc.

“AT&T continues to insist on unreasonable and extreme terms that are totally inconsistent with the market,” Viacom Chief Executive Officer Bob Bakish said in a memo to employees. “Having recently acquired Time Warner, AT&T appears intent on using its new market power to prioritize its own content at the expense of consumers, who are growing increasingly dissatisfied with paying more for less.”

Network Competition

AT&T didn’t immediately respond to a request for comment. In April, the company will raise prices on its streaming pay-TV service. The company boosted prices for its satellite TV service in January.

The phone giant completed the purchase of Time Warner last year and in the past month won a final victory over the U.S. Justice Department’s efforts to stop the deal on antitrust grounds. Since then AT&T has begun reorganizing the business, which includes Warner Bros. studios, HBO and Turner Broadcasting. The division, which operates networks that compete with Viacom, has been rechristened WarnerMedia.

Viacom shares fell as much as 3.7 percent to $26.50 in extended trading. AT&T was little changed at $30.65. Viacom was among several media stocks that slumped on March 13 following reports that AT&T would be removing channels from a reshaped DirecTV Now streaming service.

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