For years, New York residents have complained about slow and unreliable internet service while their largest provider, Time Warner Cable, insisted it was delivering speeds to match its advertisements.

But in a lawsuit filed Wednesday against Charter Communications (CHTR) - Get Report , which acquired Time Warner Cable in May for about $55 billion, New York Attorney General Eric Schneiderman charged the company with a multiyear pattern of fraudulent and deceptive practices in which millions of subscribers were knowingly deceived.

Charter, he said, delivered internet speeds that company executives knew were as much as 70% below the levels promised in its advertising.

"These shockingly slow speeds were the product of a calculated corporate strategy," Schneiderman said at a press conference held in Manhattan. "Time Warner Cable has been ripping you off."

The lawsuit, the product of a 16-month state investigation, includes numerous emails between company executives and engineers in which they acknowledged that the company's internet speeds were indeed falling short of promises. When engineers called out these practices to company executives, they allegedly were told that upgrading Time Warner Cable's modems and routers would cost too much money.

"The company could have upgraded to faster routers, and that was a suggestion made by their own engineers." Schneiderman said. "But they chose not to."

While the lawsuit only targets Charter, the largest internet provider in New York with about 2.5 million subscribers, Schneiderman said his office was also investigating the practices of other internet providers in the state. New York state, he said, is "looking for a lot of money. We're looking for customers to be made whole."

Back in July, the attorney general put Stamford, Conn.-based Charter on notice, declaring that his office was expanding an investigation into the speeds that the internet service provider said it was delivering to its customers. At that time, Schneiderman said preliminary results were "troubling."

Time Warner Cable customers have often complained about not getting promised internet speeds. The company's own chat forums hosted numerous discussions about the discrepancy between advertised speeds and actual speeds and reliability. Schniederman said his office's own test, corroborated by the company's internal studies, showed that services billed as delivering 300 megabits were often 70% slower than marketed.

In a statement, Charter, which is in the process of transitioning to the Spectrum brand, said it is continuing to invest in Time Warner Cable's service area and shouldn't be held responsible for the functioning of a system it has only had a handful of months to upgrade. By acquiring Time Warner Cable, Charter gained some 13 million new subscribers in markets that also include Los Angeles and Dallas.

"We are disappointed that the N.Y. attorney general chose to file this lawsuit regarding Time Warner Cable's broadband speed advertisements that occurred prior to Charter's merger," the company said in an emailed statement. "Charter made significant commitments to N.Y. state as part of our merger with Time Warner Cable in areas of network investment, broadband deployment and offerings, customer service and jobs.

"We will continue to invest in our business and deliver the highest-quality services to our customers while we defend against these allegations involving Time Warner Cable practices."

Yet even though Charter didn't own Time Warner Cable prior to July, it could still be held accountable if a court rules that its actions were fraudulent, said Michael Connor, executive director of Open Mic, an advocacy group focused on internet privacy and affordability.

"When you buy the assets, you buy the liabilities," Connor said in a phone interview in New York. "Most anyone in New York City or state where Time Warner Cable does business knows that the substance of the attorney general's lawsuit has merit. The big question is whether it will get any better under Charter or Spectrum."

The lawsuit could serve as a warning to the country's internet service providers that legal action will be taken to ensure that broadband services, which have become an integral part of daily life, perform as advertised. Broadband deployment is expected to be a high priority of the Federal Communications Commission under incoming chairman Ajit Pai, a Republican appointee.

"These issues are not exclusive to Time Warner Cable," Connor added. "You hear about them all the time. What's truly disturbing is that Time Warner Cable was refusing to invest in its own network at the same time that it was negotiating a very lucrative sale, which resulted in multi-million dollar bonuses to all of the top Time Warner Cable executives."

Robert Marcus had been Time Warner Cable's chief executive for 16 months when Charter closed the deal to acquire the country's second-largest internet service provider. The largest provider is Comcast (CMCSA) - Get Report , which attempted to acquire Time Warner in 2015 until the deal was rejected by the FCC under former chairman Tom Wheeler, a Democratic appointee. Time Warner Cable was spun-off from Time Warner (TWX) in 2008.

Marcus, who held the position of chief operating officer from December 2010 until being promoted to CEO, received a severance package of approximately $92 million as part of the company's sale to Charter.