Not Wanting to Assist

I return 2 items that had been purchased 16/3 at Design Quarter to Cresta on 19/3. I had paid with RCS card. I was t5old my account cant be credited but I can get a voucher for R258 which I accepted. Today 26/3 I had a smash and grab and call store to cancel voucher (card & Slip for voucher are in the bag that was ******) and am told there is nothing we can do. How is this possible when you sign a handwritten control sheet saying you were issued with a card and its number and they give you a receipt showing that a certain card was credited to the voucher, which they keep a copy of. <br> Is this true or just laziness???? Thanks to them I am now more out of pocket as account wasn't credited and voucher cant be cancelled!!