No money to refund

I bought curtains at the Gezina Galleries Branch of Sheet Street to the value of R1,349.95. I paid with my debit card. Unfortunately the curtains do not fit my windows therefore i return them to the same branch and ask for a refund. To my surprise the answer was that it is not possible, reason, we have not enough money, NOT R1,349.95?? I need the money back, can someone please explain when this can happen? as not one of the nearby branches had any money.