Clicks Guguluthu square selling expired chocolate

I bought a Nestlé KitKat chocolate at Clicks Guguluthu square today, when I got home I gave my child 1 bar and I took 1,it was not crispy as and I checked the best before date. It was expired on the 31/12/2024.i took the chocolate and the slip to clicks Junction mall because it closer and I wanted something there,the manager told me to go back to where I bought the chocolate. Can you please assist as I already consumed the expired chocolate with my daughter. I still have the chocolate and the slip.