At the age of 55, Jean-Pierre Voidies had a sex-change operation. He had been a political activist, poet, novelist, husband of the bird-like Huguette Voidies and the father of one son, Jean-Noel. By his own account, Mr. Voidies was a member of the Underground during the Nazi occupation of France and was tortured by the Gestapo. Today Ovida Delect, the former Jean-Pierre Voidies, is a dainty if strapping older woman, with the physique of a steam fitter and a voice to match. She's still a political activist, poet and novelist as well as the author of an autobiography, ''Putting on the Dress.'' No longer the husband of Huguette, she is, instead, Huguette's life-long companion and the cause of quite a lot of contradictory emotions in Jean-Noel, an earnest young man who continues to live at home and hopes to become a professional disk jockey. Ovida Delect, both as she is and as she would like to appear before the world, is the subject of Francoise Romand's ''Call Me Madame,'' a wonderfully oddball, 52-minute documentary. Miss Romand makes documentaries that look like those of nobody else. Though she sticks to facts, they're often facts that few writers of supposedly serious fiction would dare to touch except under pseudonym. ''Mix-Up,'' which introduced Miss Romand at the 1986 New Directors/New Films Festival, examined the tragicomic results of a long-running (20-year) real-life farce, begun when an English nursing home switched two babies and sent each mother home with the other's child. If Miss Romand never seems to be ridiculing Ovida Delect, part of the reason must be that Miss Delect is such a forceful, enthusiastic collaborator, running the movie in much the way she runs her household. From her remarks about her politics and her activism, it's clear that she is not a nut. She's an unbudgeably self-confident presence. (Vincent Canby - NY Times)