Refusal of a refund by the company

I bought a ring at Sterns in Kroonstad worth R2,100 on the 18th of June 2015 cash. I wanted a gold ring but they sold me a ring with gold and silver on it. Upon realising that, I immediately returned the ring to the shop. I was given an option to take another ring. I looked for the one I wanted but I was not interested in any of their other rings. I asked for a refund and was told that no cash was available so I should take the ring to one of their shops in Gauteng. When I got to Gauteng shops I was told the same story, that they do not have cash. So the shop is refusing to refund me for the ring I do not want.