Outstanding Refund

It was on the 16 February 2016 when I bought vegetables at Housewives market then I paid with my card and the cashier billed the butternut twice by a mistake then I asked to be refunded. They said it will not be easy by cash it has to be reversed back to my account so I paid cash by cash and card following their instruction. They said my money will be reversed within 24hrs which didn't happened till now. After that I went to them about twice still I haven't been paid till today and they don't make any follow up to check whether I got my money or not. I phoned the manager Sonjay on *** the other day and he continue with empty promises that my money will be paid. They got my bank details and my phone number I still got the cash slip with me as a proof that I paid twice for the vegetables. I want to be refunded my R334.94 as I ended up paying twice.