Won't replace broken appliance

I spend approximately R100k per year at this branch for my groceries. Last week we bought a hairdryer for R170 - it worked twice and then stopped working. Unfortunately I can't find the slip but I still have the box. They won't replace the item for me without the slip and they won't even take it to the supplier to be fixed. So there is only one solution - I'll take my money to their competition which is 2 doors away. Such stupid thinking by their manager!!