Rude cashier

I went to buy clothes at Mr price Sammy marks, there was a buy one get the cheapest one free on red tag clothes. I was assisted by Busisiwe Mahlangu as stated on her name tag, the lady game me a attitude because my items added upto R240 and went upto R460 when she added gift bags (they were R10 each and I bought 3). I refused to pay the money, and asked her to check what the problem was, she told me to step aside for her to assist her customers. After few minutes she called her manager, because there was a guy who needed to buy a gift card with an account.

The manager then asked why I was not assisted, I explained everything to her. Busisiwe suggested that I leave the gift bags, the manager told me to go get another bag since they were 3 and that was the reason for the high amount. When I came back to pay Busisiwe to me to wait for her to assist another customer because she doesn't want to cause any problems with them. I've never been so belittled as a customer before.