Rotten Ox Liver

I am disappointed on the Ox Liver I bought at Pick n Pay the Bridge in Johannesburg CBD. I bought it on the 18th of December 2018 I can't recall the time but it was after 16:00. When I cooked the liver it was off and tasted very sour. Unfortunately I do not keep my grocery slip but if they can check their duplicate they will see that I bought the liver during that time. I bought it with Lean Mince, Doodle Duckin and a plastic. I want to know why did they sell me rotten meat I am very angry.