I've used the call button maybe three times in all my flying. Was ignored every time.

Once on a NW flight to NRT, a young Japanese woman had inadvertently pressed the call button. The FA who came by to answer it reacted quite angrily and ripped this poor woman a new one, telling her she shouldn't use the call button "unless you're having a heart attack!" (FWIW, she was the worst FA I've ever seen and was antagonizing basically all the passengers throughout the flight.)