get your wires crossed
From Longman Dictionary of Contemporary Englishget your wires crossedget your wires crossedCONFUSEDto become confused about what someone is saying because you think they are talking about something else → wireExamples from the Corpusget your wires crossed• Somewhere along the line, some one had got their wires crossed, that much was clear.• We got our wires crossed and I waited for an hour in the wrong place.