Return not collected and no refund

I returned a cot mattress on the 24th of December. It has not been collected till today and I have not received my money back. I keep getting an sms that collection will be done on a certain day, when that day comes I get an sms saying the collection has been delayed and that they will reschedule. The same thing has been happening since the 24th of December. The people I've been talking to on email are also as useless. I just want my money back.