OXFORD freshmarket Hillcrest has the world's worst supervisor with a stinky attitude!

I went to Oxford freshmarket in Hillcrest for shopping. I was happy with the quality of their fresh produce as always and the prices were the best ever. However after paying for my groceries I noticed that the total amount I had to pay didn't corelate witn what I had bought. Upon checking the slip I realized that the cashier had charged me R89 for a butternut bag instead of R25 and I had bought 2 of these bags. I went back to the store and asked for a supervisor. The supervisor (some colored/indian lady) came to me and I explained to her what had happened. At first she tried to force me by saying it was my msitake: that I had taken a 10kg bag instead of a 7kg one...We went to check the stock and it was so embarassing to realize that there was even no 10kg bags in stock (so the supervisor doesn't even know what is on stock...). So after this embarrassment, she took me to a till where I was refunded R127 or something like that. All the time she was handling this matter you could see that she is very not interested, like I irritate her or something. She didn't bother to offer me an explanation or even an apology... I asked her if she is not going to explain what happened and she said the cashier probably used a wrong code (PROBABLY) and that was it. I don't understand how someone with such a stinky attitude can be made a supervisor. If a supervisor can't show any respect to customers, what lesson is the staff learning from such? The lady was just disgusted the whole time and I was very disappointed just to say the least because OXFORD is a terrific supermarket and all but it was like the lady is out of place or something like she belogs in a store that sells attitude NOT food.