In retail, was there ever an upset customer that you had to handle? How did you deescalate the situation and make the customer happy?

I was asked to bring home a stack of 10-15 greeting cards and memorize the 4 digit number on the back of each card for my next onsite interview. When I returned the owner showed me the front image of each card and had me list the 4 digit card number from the back. Very easy and understandable figuring all of the inventory needs to be memorized in order to be efficient and successful in this field.