Refusal to pay back deposit

My contract with Ritzy rentals ended November 2015. I have done all the exit evaluation and left the flat as new like I found it. But to my surprise Ritzy is refusing to pay back my rental deposit of R10000. It's now March and still they haven't refunded my deposit. They are not replying my emails. Their phone rings without being answered and the agent number when called it says the number no longer exist. Please someone help. Is there a place where I can lodge a formal complaint.