get hold of the wrong end of the stick
• misunderstand something.
Similar:
misunderstand,
misinterpret,
misapprehend,
misconstrue,
misconceive,
mistake,
misread,
take amiss,
get the wrong idea,
receive a false impression,
be under a delusion,
be at cross purposes,
be barking up the wrong tree,
get the wrong end of the stick,
