Ridiculous after sales, refuse of refund for one corner with water, box and item undamaged!

Bought a vanity set at CTM a week ago, decided to return for credit as the vanity was too small and wanted to exchange for a bigger one. To my surprise, the box with the mirror had a small corner that has water on it, its been raining the whole month and we collect from CTM with wet boxes all the time and never complained. They refused to refund the mirror due to the one corner being wet, the entire packaging and box is fine and undamaged, the item is undamaged. This is just riduclous, we have now asked for a refund as we will not be using the credit for exchange as we will never be buying here again, we have bought at CTM many times for many house renovations, but never again.