Be careful, ensure the shop assistant is packaging your goods in front of you

I bought 24 blue mugs from a Sheet Street in Springs. When I got home, Surprise, surprise it’s only 20 mugs! I checked my slip to ensure whether I paid for 24 or 20. It was definitely 24! I called the store since the person who assisted me packaged them under the counter, asked if there aren’t any left and the answer was no. I was told I would be given only 3 white mugs since that is what is left from their shelf. I had to drive to the store and was given the 3 white mugs. What an inconvenience!!