Disgusting cashier

I had the most humiliating experience in a very long time. I visited a Dischem store in Alberton New market today 24/08/2019, and everything was going well until I got to a till. I was with my mother so I did not want to cause a scene because she's a sick lady. I approached a lady who was sitting at till 7 because I wanted to pay and just get out of there and was told by this woman who's job is to check out my buys that she has already called another person to her till and basically I need to make another plan. The person who she supposedly called was 3 people behind me and I could not fathom how a person behind me has more of a right to pay thane who got there first. She is disgusting and needs to be called into other. I need an apology or else I will be taking this further. She has messed with the wrong lady. Is this the type of behavior that dischem condones and tolerates? What a bitter end to my beautiful day.