I actually had a similar situation. I found out I had a neighbor stealing my wifi a few years ago because of BT shenanigans.
I gave the guest wifi pw to the previous neighbor, who must've written it down somewhere. The new neighbor was a douche who kept piggybacking off of it to watch stuff with his shitty little kid, so I'd occasionally get notifications on my network. When I confronted him about it, he got belligerent and threatened violence.
So I paired to his device and blasted porn at full volume.