Angry loyal customer

I Bought Bakers Tennis biscuits in a Shop in Johannesburg CBD This morning 02-Feb-2015. I always buy a pack in this shop every morning, and I always check expiry date, this expire in September 2015, when I got to work opening the pack the cakes were off and eaten by insects and had blacks spots as if its insect waste. I had to complain about this in case I don't get a pleasing response from supplier.