Black Friday sale **** -overcharged

Worst online shopping experience ever ‼️‼️‼️It was my first and last time ever buying from them online😡. I know now why customers are irate. You sell something on special, they charge you the full s as amount but the system doesn’t prompt for smart shopper number to be inserted before checkout is finalised . How is that treating customers fairly. I will be lodging my first complaint with Ombudsman’s .