Service complaint at RiverSquare

Good day, I purchased items at Pick ‘n Pay Clothing River Square in August 2019. I returned one of the items on the slip at another store shortly after making the purchase, but never received my slip back from the cashier. At that time, the cashier who helped me with the return at the other store, advised me that the other items can be returned or exchanged as long as the price tags are still attached to the item of clothing, without the slip. Yesterday afternoon, I went to the River Square store to return the top. I was told that I cannot return the top for a refund as I do not have a proof of purchase, I can only exchange it. I picked another item of clothing for the same price and went to the till to do the exchange. The cashier advised me that they will only be refunding me half the price because the item is now on sale (since 2 September 2019). I told him that I had paid full price as per the tag on the item, which is still attached to the top, and the tag has not been marked down or have any stickers on to say that I had paid a reduced price. He called his manager to assist. The “Manager’s” name is Mariaan. She advised me that because I do not have a till slip, they cannot refund the full price and only the special price which it is currently loaded on the system for, and that she cannot override the system. I told her that I find this unacceptable as I have followed the returns policy (returned within 30 days of purchase) and that I cannot be held responsible for the specials they are having. She said that I will get a full refund if I produce the till slip. I explained that I no longer have the slip because I had previously returned another item to Pick ‘n Pay. I told her that I was not leaving the store until I had been helped. The Manager, Mariaan, rolled her eyes at me, told the cashier to carry on with his work and to leave me standing there, if I want to wait!!! She walked away, proceeded to sit down on a chair behind the till area and the cashier took the trolley full of clothing and carried on with his work. I then demanded my goods back and told her that I would be logging a complaint and she said it is fine. The treatment of customer’s is unsatisfactory. Also, the unwillingness to help even though I have a legitimate reason for not having my slip!!! It is in Pick ‘n Pay’s possession!!!!!! I want my money refunded for the item of clothing purchased!