Bad customer service

I visited the store on the 27th of March and bought one item of R35 and gave the cashier R100 so while she was processing the transaction she was busy

Chatting with the next cashier and before she closed her drawer I asked her how much the item I've bought because I can see she is giving me the wrong change which is R15 instead of R65, That's when the fight starts because as the cashier you the one who's supposed to check the amount they giving you The lady said to me are you sure that you gave me 100 so what does that mean if you are the customer she was busy Telling me that I'm young and I should take my staff and go when I go and report to the till supervisor she change the story that I shouted at her and to me it seems as if I'm the one whos wrong because I simply told her that if you think I'm Robbing you, we can go and check the camera because how can me ask me if how sure iam that I gave you 100 while you think I gave you 100.So this cashier gave me a bad service and I was so cross because according to her I'm not the customer I'm just a young person who want to rob her. The cashier was Chrishelde Pheme