Bad attitude received from cashier

i bought a family treat 8 pieces and when i got home i found that they only put 6 pieces. I went back to complain and the cahier that assisted me told me that it was not her fault but the person that put the order into the bag and she told me that it was my duty to check if my order was correct before i left the store. i was very angry and asked to speak to their manager and i was told that there was no manager and needed to come back and complain when the manager was available. Im so disappointed about the service i received from KFC and this was not the first time that i received bad service from them