Filed at 3:09 p.m. ET NEW YORK (Reuters) - AT&T Corp. (T.N) on Wednesday saw its credit ratings, affecting $25 billion of debt, cut to two notches above ``junk'' status by Moody's Investors Service, which said the company faces ``weakened revenue prospects'' and rising competition in its core business. The cut triggers a rise in interest costs for the New York-based long-distance phone company, the nation's largest. AT&T became the latest big telecom in May to suffer a credit rating downgrade. Its largest rival, WorldCom Inc. (WCOM.O), was cut to junk status by all leading U.S. rating agencies, while Qwest...