My problem is the reverse from the original question in the Sonos community that I found while trying to research the issue, “I can play to my neighbour's Sonos system via Airplay but I'm not on their wifi - should I be able to do this?”

My neighbor deliberately connected his speakers to my Sonos and he is also able to play my own iPad music through his speakers. If try to play my own music on my iPad and if he has his system turned on, my music will blast out loudly through his system. He can turn the volume up or down and can turn off My Music on my iPad. 

One day a couple of months ago, he took his laptop into the kitchen (directly above my kitchen) while I was listening to music on my Sonos in the living room. He was tapping keys for several minutes.  It was then, a few days later, that problems began for me with my own music. I first had cheap Bluetooth sleep headphones and one night all of a sudden, the music that I was listening to on my iPad was turned up very loudly in my ears but I also could hear it when I took them off because it also came through his speakers. We have no soundproofing so loud music from his speakers pounds through the ceiling. I then deleted the Bluetooth sleep headphones and bought wired ones. I thought that there was no way he could do this with wired headphones. Wrong. He still can do it. I can’t use them to listen to music to go to sleep any more.

i then tried sleeping in my living room where I have my Playbar and two ones. I left it on to go to sleep but he turned it off some time during the night so I can’t listen to music on my Sonos either if he has his own system on.

i hired a “tech specialist” that told me that this was impossible that no external person can control my music. The tech guy changed all of my Wi-Fi passwords and on the router and he thought that this would solve the issue but it did not. The tech guy was not a Sonos expert and I don’t know if this impacted his ability to solve this.

The neighbor will not undo whatever he did (I’ve asked) and I don’t know what to do to fix it on my end. I’m older and not tech-savvy. The HOA will not demand he change this if they don’t even understand what he may have done. Can anyone explain or give me direction, I would be very grateful. I will also use an Airplay tag to post this because I’m wondering if he somehow did all this through Airplay? Thank you in advance and I hope this makes sense as I have written it.