Discourteous sales girl

I bought a pair of $22 tights that had to be returned because they couldn't get past my toes. I rushed over the next day to return them for exchange. But they said that was impossible cos it was a final sale and I had worn them; which I hadn't. I didn't know it was a final sale because I can't read French and I wasn't told. We also checked my fit based on height, not on weight which would have made more sense. The sales girl I met the previous day was nice about it but there was this unruly sales girl that kept on raising her voice to say there was nothing they could do. I kept on telling her that I wasn't talking to her. But she wouldn't listen, saying I had to leave with expensive tights that I couldn't use. Finally, she started screaming that I was yelling at her, while I wasn't. At the end of the day, the nice sales girl called the manager and the tights was exchanged. But by that time, I was already in tears from the humiliation at the store. I wondered if I was treated that way by the other girl because I am Black. I have never had such a humiliating experience.