US WEST Inc. agreed Friday to pay a $10 million civil fine for violating the 1982 court decree that broke up the Bell System. It was the largest fine ever levied in an antitrust contempt case.

In documents filed with the U.S. District Court for the District of Columbia, the company admitted to four violations of the consent decree. The order required American Telephone & Telegraph Co. to spin off the regional Bell companies and restricted the types of businesses and services in which they may engage.All of US WEST's violations took place between 1985 and 1989. The infractions included:

-Offering a reverse directory service in which the customer receives the name and address of a telephone subscriber rather than the number.

-Providing, through its Applied Communications Inc. subsidiary, computer hardware, staff and other support to run a debit card system for Atlantic Richfield Co.

-Offering the General Services Administration a lower price on local exchange access if it purchased switching equipment from US WEST instead of AT&T, which amounted to illegal price discrimination.

-Violating the ban on manufacturing telecommunications equipment. US WEST designed and sold operator work stations for director assistance and call-assistance operators through its Knowledge Engineering Inc. subsidiary.

US WEST lawyers said the company, based in a suburb of Denver, did not willfully violate the 1982 agreement, and company officials said that the complexity of the court decree had made it difficult to follow.

US WEST's chief counsel, Larry DeMuth, said that by signing Friday's agreement, the company avoided a lengthy and expensive legal battle.

US WEST operates Mountain Bell, Pacific Northwest Bell and Northwestern Bell.