Not Promoting Decent Behavior

(I am working the front at a fast food restaurant. I am ringing up two ladies (mother and daughter) up. They are regulars.)

Me: “Hello, how may I help you?”

Daughter: “Hi, I have this coupon: buy one get one free breakfast sandwiches.”

Me: “All right, which sandwiches would you like?”

(They order two sandwiches, one more expensive than the other. I promo the more expensive one off.)

Daughter: *to mother* “Haha, she only charged us $1.69!”

Mother: *mockingly* “Smart employees!” *snorts*

Me: “I did it to be nice, but I’m definitely not doing it for you again.”