Insulting and offending customers

This morning I went to Spar Jean Ave to buy Vetkoek and mince, juice and smokes. When I got to the till Sharlotte served me and as she was scanning my goodies she asked her colleague in Sotho what is this referring to my vetkoek and she was told it's a vetkoek.Then she exclaimed in Sotho that (Kea hlanya ke tlo reka legwinya la R22) which translates to I am going marbles or crazy to buy a vetkoek for R22. I almost lost it but I kept my cool and asked her so do you mean I am mad to buy what I feel is value for money and they both giggled until I left. Personally I think Sharlotte should be shown the door but considering our country's high unemployment I think my sister needs training or to be disciplined somehow.There is so much one can take from these cashiers she could have said that to her colleague in my absence not while I was present in a language that I understand..I mean really Sharlotte ,please Spar management look into this.