Shit like that is always so frustrating. I don't have any legal advice, but start hounding those fuckers until actually fixing the problem becomes less of a hassle for them than dealing with you.
I had a number of issues with a property management company where they kept jerking me and my wife around on the phone and then never followed through. I drove over to their main office, gave the secretary shit until she gave me the address of the work site of the guy in charge, and went there and just yelled at him in front of his staff until he agreed to solve the issue right away.
Don't give them an inch. If the supervisor isn't doing shit, hound the office, if they aren't following through, go above that. If he said he will be there at 11 and doesn't show, make sure it becomes some higher up's problem right away. There should be half a dozen voice mails for him by now, and for anyone higher up in the company. Don't bother with texting or Email or any of that shit, make his phone ring for an hour straight if you have to until he picks up.
Fuck... I'm all worked up just thinking about it. Good luck!