False advertising

I was a loyal customer here until last Friday. They had great sales but also for loyalty members which I was, you get an extra 10% off . Which I didn't get. And when I asked the lady about it, she got very upset with me, throwing her hand up and shouting "mam please " at me even though my voice wasn't raised at her. I genuinly just wanted to know and also mentioned that its false advertising. (She added the 10% to my final amout which she then swiped onto my loyalty card which came out to less than half of what my 10% would have been) She then shouted at the other lady, June, to just refund my 10% I am supposed to get back and then give it to me. Which I then told her that I didn't want it and I'll shop elsewhere.