Refusal to give rightful customer refund

My father purchase a walking ring for my daughter on Monday 22 February 2016, it was assembled in the shop and the box was left behind. we then discovered that the walking ring was not the right size for the baby and decided we needed to return the walking ring. We took the walking ring and presented a slip at the shop and we're told by the security guard that we could no longer return the product because they had threw away the box. Not understanding how this was relevant we asked to speak to the store manager, Refiloe who **** and said that my father told her that they could throw the box away. This is a lie because my father said no such thing and he was not even told of such a ridiculous policy. He would have simply taken the box with him if it would have meant that we could not return the product. The manager was rude and smoky refused to attend to the matter. The product is in the same condition we received it and we have proof of purchase we would like a full refund because we cannot sit with the incorrect product