Get your wires crossed
Definition 1 of 1
Pro Tip 1/3Confusion Source
Clarify that the confusion often comes from miscommunication or misinformation. 
Sorry if I misinformed you and we got our wires crossed.
Pro Tip 2/3Resolve Mistakes
Use the phrase when recognizing a misunderstanding and seeking to correct it. 
Let's meet again; we got our wires crossed about the project's goals.
Pro Tip 3/3Casual Tone
The phrase is informal, best used in casual or friendly conversations. 
Did I get the time wrong? We must've gotten our wires crossed.