Verizon Communications will fight the “cramming” of unauthorized charges by companies such as Internet providers that appear on phone bills.

New York Attorney General Eliot Spitzer said the settlement is the first time a telephone company has been required to monitor and correct the fraudulent billing practices by other companies on phone bills. The action follows complaints about the unauthorized charges by Internet service providers and other services on Verizon phone bills.

“Verizon has an obligation to protect its subscribers from fraud,” Mr. Spitzer said Friday.

Verizon, however, already had policies to act promptly on behalf of its customers, said a Verizon spokesman, Cliff Lee.

“Verizon takes very seriously every complaint of cramming we receive from our customers and more than 99% of the time our customer service representatives handle these complaints according to the policies and practices we have in place,” Mr. Lee said. He said Mr. Spitzer’s probe found only a small number of times Verizon’s policy wasn’t followed.

Under the long-standing policies, Mr. Lee said Verizon eliminates the contested charge then contacts the company that put it on the phone bill.

Under the agreement signed Wednesday, Verizon will pay $75,000 for the cost of the investigation and notify customers in their bills of a toll-free phone number for more information. The company also will provide credits to “crammed” customers, end contracts with companies that cram, and block future charges by cramming companies.