A lawyer for American Telephone & Telegraph Co. asked a federal appeals court today to overturn a jury's award of $1.8 billion to Mci Communications Corp. in a antitrust verdict.

Howard Trienans, AT&A's general counsel and chief of the nation's largest corporate law force, told a three-judge panel that the case never belonged in federal court, charged that MCI had "concocted" a damage study and suggested that AT&T has been a victim of an MCI plan to manipulate government regulators.

On the other hand, Chicago lawyer Chester Kamin, representing MCI, called the landmark case a "classic" antitrust case involving AT&T business decisions to limit the ability of MCI -- now the nation's leading long-distance competitor to AT&T -- to grow during early 1970s.

Oral arguments on the appeal, which AT&T said it would file immediately after the decision was announced, came today in a tense courtroom filled to standing-room-only capacity. The judges gave no indication of their intentions in the case, and asked few questions, focusing on defining industry lingo and seeking citations of evidence presented during the trial.

The three judges are expected to release a decision as early as late summer in the appeal of last June's verdict. The jury decision in the six-year-old case resulted in the largest antitrust penalty ever levied and is but the first of two antitrust cases brought by the District-based company against AT&T.

The jury concluded that MCI was entitled to $600 million in damages, two-thirds of the amount the company sought. Under federal antitrust law, such penalties are tripled. The jury found AT&T guilty of 10 of the 15 violations it was presented with after U.S. District Judge John Grady threw out another 7 charges.

Trienans said the case stemmed from a period of "confusion and turmoil" in the early 1970s immediately after the Federal Communications Commission began to break AT&T's historic monopoly over long-distance calling services and open the business to competition.

Trienans contested the MCI charge that AT&T acted anticompetitively in its announcement of a cut-rate Hi-Lo tariff, saying the move was but an example of AT&T's efforts to compete. "Aren't the antitrust laws supposed to encourage competition?" Trienans asked.