Returning of soured boxed wine purchased three months ago goes wrong never opened

3 months ago I purchased 10 boxes of 5lt Roberson Ruby Red Wine at Pick'n Pay Hypermarket North Gate shopping center where I have been doing my shopping for the past 19 years. My wife and I are retired and we always try and buy in bulk to save us from going back and forth. Also every month we have been spending between R5000.00 and R8,000 for groceries at your store. Now today I went back to the pick'n pay store to return 6 of the boxes of wine that went sour. I was told I needed a receipt, but unfortunately I have missed placed it and can not find it. So I placed the 6 boxes of wine onto their counter and told them to take it for free and that I will not come to another Pick'n Pay store again unless this is resolved. After so many years of loyalty this is how I am treated.