When you hang up the phone without indication. Typical people will give some indication the conversation is over, "see you later," good bye," "talk to you soon," etc. But as Hollywood movies have taught us, this is not necessary. When you are finished with what you have to say, hang up.
-"Did you get the memo I sent you, Rob?"
-"Yes, but I will read it later."
Jukebox sabotage is a form of implanting one's own music into another person's mind by singing or whistling a tune around that person. If successful, that person will then begin whistling or singing your song minutes later.
I whistled "Mary had a little lamb" around my friend Matt one afternoon and then 5 minutes later I heard him whistling it down the hall. That is a textbook Jukebox Sabotage maneuver.