AT&T Co is howling to the Federal Communications Commission that failure on the part of MCI Communications Corp to file interstate tariffs for services to Merrill Lynch, Pierce, Fenner & Smith and others has drained away revenue for AT&T and has meant that the MCI rates can’t be checked by AT&T or regulatory bodies to determine whether they are fair and reasonable: AT&T wants the Commission to award it damages that would equal the revenue it has lost plus interest.