Poor customer support

We bought an item from Makro online. We then made a reasonable request to replace the item with a more expensive one and pay in the difference. Usually online stores do this by cancelling the order, crediting your account and then making a new order where you then pay in the difference. Makro refused. We now sit with a product that we do not want yet had to pay for. Seriously Makro? You would have made much more money by simply giving good customer service?