My next door naighbour hacking my WiFi and also making his "WiFi" offensive names about me. It's kind of stalking. Those people sitting in home and only one thing what thay can do is smoking drugs. Problem is long and they still stalking. Their service provider was cancelled so they hacking me and my kids. Noone can see errors. I made printscrins of networks names arround me and one offensive about me.
You should also change your Wi-Fi password.
Then if I were you report them since they are being abusive and effectively stealing from you.
If want you can also call the broadband team to explain the situation. See link for number.