How to take action against owners association management company?

Don't want to publicly name and shame so let's say my building is managed by a company X. There's a massive leakage coming into my apartment from the one above who's running an unauthorized sharing apartment! I've tried complianing to X first, they sent me a inspection report and emailed the owner but didn't do much beyond!

I registered a complaint with a couple of agencies which forwarded it to this company X and closed it after inactivity!

X never answers my calls on time, takes ages to reply to emails and now here I'm stuck repeatedly fixing my ceiling which gets mold every week due to the constant leakage!

I contacted a lawyer who said no point continuing unless X cooperates!

How do I now make sure company X takes me seriously and gets this resolved?