Couldn’t return once-off worn shoes

In the morning my aunt came looking for size 12(kids) at the Grove mall, Woolworths and they referred me to Woodlands Mall. When I got there they told me they don’t have a size 12 for the pair of shoes I wanted to exchange, then came back to the Grove Mall to refund the shoes and they told me that the shoes should be in a “sellable condition” and my aunts child only worn the shoes once(my aunt then checked before going to Woolworths whether or not the shoes were damaged and they weren’t)and now I cannot return those shoes, because they refused