"The Love Box" is one of the more tedious examples of '70s smut I've seen. IMDb doesn't list it as a comedy - it doesn't list it as anything - and this is correct there's nothing in it that could be taken as funny: none of the usual silly music and people falling over or nakedness used as a punchline.
Another lame British sexploitation film from Tudor Gates (I previously endured his INTIMATE GAMES). This is the guy who scripted Hammer's rather fine female vampire trilogy before moving on into the murky waters of the British sexploitation film genre.
The Love Box is the product of an era when exposes of unorthodox customs could guarantee a large and curious box-office. It's look at the world of small ads having obvious commercial and actual debt to Derek Ford's The Wife Swappers (1969).