bad service and Rotten foods

I'm totally disappointed/disgusted with the level of service I received from checkers, on the 16th December I bought a cake and the sell by date was the 17th December, however to my surprise the cake spoiled not understanding whether the dates were tempered with or what. it's not normal for the cake to be in such a condition before the expiry date. I'm totally disappointed and never going to purchase another Item from checkers.