They won't pay me back my money

I had an RCS Loan which I had paid the final installment in Sep/Oct 2017. After having paid, I actually realised that I had paid in an extra installment. I started the process of requesting a refund in Nov 2017 and eventually in Dec 2017 was finalised and they said that I would be refunded by 22 Dec 2017. Well, the 22nd Dec came and went, and I called the next week and the week after and so on. Still promised that I would be paid the next Friday and then the next Friday.....this is so ridiculous. This is my money, yet I need to beg for it. Yet, if the roles were reversed and they were looking for their money, they would have hounded me everyday until its paid. Their call centre waiting lines just to get through, you are waiting for 20 to 30 min, then on more that two occasions when I had eventually got through, the agent placed me on hold for almost an hour on those occasions. It costing more to get my money back. I am so disgusted at their treatment of their clients. The refund is not even that much. I am so sick and tired of being pushed from pillar to post. All they do is tell you lies, one after the other.