Poor Quality

I purchased a duvet cover and inner which I used for less than a month. It started getting patches before I could even wash it. The inner had so much fluff coming out from the inside. I took it back to the store, Alberton New Market Mall, for evaluation. They sent it back to the warehouse. I was called and told they can only exchange the inner as it had a factory fault but cannot exchange or give me a refund for the duvet cover as I might have damaged it either with the fragrance or lotion I use. My question is, how come the sheet I sleep on, which was also bought from the same store is not damaged, but the duvet covers only? The staff on call and at the store were rude and not professional. Can I get a refund for the products I purchased? I'm not happy with the quality. If the inner had a factory fault, clearly the duvet cover is also poor quality.