I am glad you confronted them. Don't hold back, and don't get personal. 多confront 几次就练出来了.都说吵架最练英语了!Sometimes One-on-One talk is necessary. People don't get along because they don't know each other better. Try not to get too personal when confronting others. Good luck!
You reminded me of a Chinese lady working in the Macy's,she was new, but she was very nice and helpful and she showed me how to combine those coupons. I wrote a very good review for her in Macy's survey right after I got home.
请多写!