Builders warehouse bad customers service - Won't exchange product

Builders warehouse customer service is so bad these days that I have decided not to buy from them anymore. On the 17 Dec I spend close to R1400.00. I bought a circular saw plus a blade for this saw. The sales person recommended this blade for the circular saw. The same day I opened the packaging of the saw but did use it that day but 2 weeks later I decided to use it only to realize that the blade won't fit because of the whole in the middle is to big. I went back to builders to exchange the blade but they refuse the help me because of the packaging. I would understand if only spend the R200.00 on this day but I spend close to R1400.00 that day. The way I feel right now is to go back to the store and by accident damage a view items to justify Builders warehouse action's.