I did similar. 6 months after moving out of a flat, we hadn't received our deposit, apparently because the landlord lived in the States and they "couldn't get hold of him". Additionally, our property manager seemed often to be out of the office when I called and never responded to an email. Ultimately I threatened them with small claims, combined with a concerted PR effort to let all media and social media know what an utter bunch of c@nts they were, and an appeal to their regulatory body (sorry, can't remember off the top of my head what it's called but I found it through an online search and they are supposed to regulate this kind of thing quite tightly - I quoted at least two regulations that they were in breach of). I copied in the CEO of the company as well as my property manager's boss and within a week I had a cheque for the full deposit. It took a ridiculously long time, but had I thought of all / any these things at the outset, it would have taken considerably less than 6 months. Good luck - I sympathise massively, I know how time consuming and hopeless it can seem, but I think that if you can show them that you know what you're talking about, they may suddenly remember that they might be able to help after all.