The attorney general of New York is suing Charter, just months after its mega-merger with Time Warner Cable, for allegedly failing to deliver the internet speed and reliability it promised to millions of customers.

"The allegations in today's lawsuit confirm what millions of New Yorkers have long suspected: Spectrum-Time Warner Cable has been ripping you off," Attorney General Eric Schneiderman said at a press conference.

Charter has rebranded its cable and broadband services under the name Spectrum.

Schneiderman said Charter's failure to deliver on promised service was no accident. He accused the company of having conducted "a deliberate scheme to defraud New Yorkers."

Charter Communications (CHTR) said the lawsuit unfairly blames the company for actions taken by Time Warner Cable prior to the $65 billion merger, which closed last May.

In a statement to CNNMoney, Charter said that the lawsuit is about ads that Time Warner Cable ran before the deal. The company says Charter made "significant commitments" to New York state as part of the deal with Time Warner Cable to invest in its broadband network, customer service and jobs.

Charter owns Time Warner Cable and another operator, Bright House.

Related: Charter merges with Time Warner Cable

"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," Charter said in the statement.

But a spokeswoman for Schneiderman said that despite the rebranding, Charter has not dealt with underlying hardware and network problems. As a result, customers are still experiencing the same problem of "slower speeds when they're paying for more."

The attorney general is seeking restitution and said the company has 2.5 million subscribers in New York.

Time Warner Cable was a unit of Time Warner (TWX), the parent company of CNN, until 2009. The two companies are no longer related.