selling damaged goods

We bought a watermelon at Pick n Pay Middestad (Bellville) for R20 only to find that it was rotten inside we told customer care since we are going to Canal Walk we would like to get our refund from their store. They (canalwalk's pick n pay) rep**** via customer care by indicating that they do not stock that product hence will not be able to refund us This suggests that we should now drive all the way back to Middestad Pick n Pay for our refund. It is very sad to think that Pick n Pay is not willing to make the customer their first priory and that its ok to inconvene their customers. In addition, their had the audacity to inform us via customer care to take the rotten watermelon back to their store... (why didn't they offer to come and collect it?)