Showtime chief exec Matt Blank didn’t quite get the reception he expected yesterday at media power lunch mecca Michael’s, where he was heckled by other diners as he arrived. Onlookers say Blank was met with a barrage of comments about CBS’ dispute with Time Warner Cable, which has blacked out CBS and Showtime in New York. One heckler said, “I want my Showtime! . . . And my ‘Dexter,’ ” while others were more encouraging, yelling, “You’ll get through this.” Diners offering a ribbing or support included Jerry Inzerillo, Conde Nast’s Dawn Ostroff, Star Jones, Corcoran’s Deborah Grubman, and TV talent lawyer Bob Barnett dining with NBC Universal News’ Pat Fili-Krushel.