Chillies put in pizza after specifically asking not to

I took my mother (who is 61 and quite frail) to Cappuccinos Mall of the North. She ordered a pizza from the menu, and I specifically stated to the waitress that it should have no chillies in. When it came, my mother ate a slice and then started to cough violently. When I managed to calm her down, I ate one slice myself and noticed my mouth burning. On closer inspection I found sliced chillies covered by the cheese. When I complained to the waitress, her reaction was to call me over to the computer to show me that she had captured the order without chillies. As she was implying that I was lying, I just paid the bill and left with my mother before really losing my temper. The waitress offered to do a take away with the pizza, which was senseless as we did not want it with chillies in the first place. I understand that mistakes do happen, but I find the manner in which this was handled unacceptable. I would rather take my business elsewhere.