The chairman of the Federal Communications Commission will request an administrative hearing on the proposed $39 billion acquisition... The decision by the chairman, Julius Genachowski, puts a second large roadblock in front of AT&T, the nation’s second-largest wireless phone company, in its effort to buy T-Mobile, the No. 4 carrier. In August, the Justice Department filed a federal antitrust lawsuit to block the merger, saying it would stifle competition.