In English, you can use this colloquial expression, as in:
Tu dis que je ne te fais pas confiance ?!
You have it backwards (there)!
Le locuteur entend par là que
Au contraire, c'est toi qui ne me fais pas confiance !
By using the expression “you have it backwards”, you can avoid verbosity, for one thing. I’m looking for its French counterpart.
Unfortunately, « au contraire » by itself does not work here, as it is more like:
Oh que non, j’ai une confiance absolue en toi !
By saying “you have it backwards”, we expect the two elements in the previous sentence to be swapped/switched/shuffled around.