get one's wires crossed - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Also, have one's wires crossed. Become or be confused or mistaken about something, as in If you think there's a meeting today, you really have your wires crossed; it's not till next month. This expression transfers a wrongly wired telephone or telegraph connection to human misunderstanding. [Colloquial; early 1900s]