Shoe City Boots Ripoff

In March I put a pair of boots on lay bye at a Shoe City located at Greenacres Mall in Port Elizabeth. I put down a R100 deposit. I came back a couple of weeks later and paid the rest of the lay bye which was R399.95. I had since lost my original receipt but the cashier said it would not be a problem, as long as I had my ID Book. I produced my ID, paid the balance and took the shoes home. I showed the shoes to my mother who did not like how the shoes fit around my shin area (they were creased and not laying flat) so I decided to take them back and get a better fitting pair. When I went to the Shoe City store I was told that I cannot return the boots because I do not have the original slip which has the barcode of the shoes that I bought. When I was paying the lay bye for the shoes I had asked the cashier who helped me what the store's return policy is and she told me 30 days but made no mention of the fact that I would in any case not be able to return the shoes as I had no original receipt for them. The shoes have only been worn to show how they look on and kept in the box the rest of the time. Surely they must have a copy of my original receipt because you get the customer's copy and the copy the store keeps? Another question that comes to mind is it must be in their books that a pair of boots went out so it can be accounted for in the books as being returned or is it that once the shoes leave the store and are returned without the original receipt, they are no longer the store's responsibility, even if the customer no longer wants and wishes to return them? I would like answers and a solution from Shoe City ASAP.