I would personally suggest that you go to a beis din and have them call in the offender (in this case it would be the landlord as they are responsible for who they rent to) without telling them you are going. IF they refuse to come ask the beis din if you can get a WRITTEN psak (protektzia) that you can report them and then tell the offender that you are going to call 311. Don’t actually call and see what happens (in other words, use it like a warning). IF there is no improvement even from that, then, without telling them, actually call 311.
Hatzlocho rabbah!
😀 Zuberman! 😀