Spar not taking responsibility for their brand products

I bought 4x 6pack Spar brand long life milk from Spar Moreleta Square. When I opened them, they were not off but were almost totally water with just a very slight hint of milk. BB date is 29 Oct 2022. I complained to the store but they refused to replace the milk because I no longer had the till slip. It seems the ideal way of dodging responsibility for their products. Who keeps all the slips for products purchased that long? (Several weeks)