DESPITE the wishes of his fans, Isaac Hayes will not be returning to “South Park,” where he contrib uted his basso profundo to the character Chef. “I just moved on,” Hayes told The Post’s Billy Heller. And although he admits an episode that spoofed Sciento logy – he’s an adherent – didn’t sit well with him, the Oscar- and Grammy-winning Rock and Roll Hall of Famer also said he felt shafted. Hayes said the big reason he left the show last year was, “They didn’t pay me enough.” And, “They weren’t that nice.” In town to help promote “Memphis Celebrates 50 Years of Soul,” coincid ing with the anniversary of the 1957 birth of the Stax record label, the clean-headed “Black Moses” also weighed in on today’s hip-hop music scene: “It ain’t gonna last.” Hayes, still recover ing from a stroke and in physical therapy, moved deliberately and used lengthy pauses before answering questions, but he’s ready to go onstage Saturday at the B.B. King Blues Club on West 42nd Street. “I got my voice,” he said. “That still works.”