Jason probably hacked into batfam's and his friends phones to play "Sexy Back" everytime Jason calls them.
Honestly Jason routinely hacks his family and friends with random things. Sometimes it’s personalised ringtones, other times it’s to make every phone call go straight to Papa John’s, occasionally it’s to autocorrect everything into a stupid comment/insult/pun. There’s no telling with this guy. He has no idea why anyone still hangs around him. Especially his friends, who do so voluntarily. When they confront him about it he says it’s “for practice”