Disgusting service Edgars RCS

I had a Edgars clothing account which i cancelled last year since I was retrenched! So when I was paying the account off I over paid them and now I have a credit which I cannot use at their store since my card is canceled, I went to their branch thinking they will assist they gave me RCS email address and told me they have been taken over by RCS which I emailed them so many times until they responded and asked for my ID and bank statement which I send and when I followed up with them they now they say they want proof from my Bank , but they send me my statement every month showing the credit ? Disgusting service I am demanding my money PLS because if I was owing them I was going to be in arrears and have to pay interests , I send so much trying sort this out , driving to the store and also emailing them so many times they must also pay me interests I want my MONEY