Poor customer service

I bought clothes from online on my account and I went to collect from the store in Adderly street, Cape Town. I realized one item had a factory fault, so I returned it to the store and asked the cashier if I am going to buy with the same price if I buy again and she said no it’s no longer that price. I asked why is it like that because it’s not my fault the product is faulty and they told me there is nothing they can do. I demand to buy the product with same price I bought with when it was on sale because your staff was supposed to make sure to check the items before packing them.