Bad policy

I sent a non drinker to buy me wine yesterday and they bought the wrong one. It was a 3litre instead of the 5 litre that was on special. Today with the slip still with me they refused to either refund or exchange it for the 5 litre because it's the day after even though it's still closed. Now I'm stuck with the 3 litre that is expensive than the 5 litre, I just lost my savings and for what? Why? Since when is it wrong to make exchanges? Pick n pay Northgate is the worst. Please sort that out. Please