<p>AMERICA's TV sweetheart Katie Couric got a little testy Tuesday night when a West Village doorman tried to enforce his apartment building's ban on talking on cellphones in the lobby. While waiting for a friend, our source says, Couric got on her cellphone and began blathering away. "The doorman approached her and asked her politely to take her calls elsewhere," says our spy. "It was clearly posted on a sign five feet away from where she had been yakking for nearly 20 minutes." Couric refused to wrap up her conversation and snapped, "You give a doorman a little power . . .!" The dissed doorman would not back down, however, and Couric was eventually convinced to step outside the building. "I was just doing my job," the doorman shrugged to sympathetic apartment dwellers. A rep for Couric didn't return calls.</p>