Worst Return Policy Ever!

I bought the Elektra Health warm mist humidifier from this store, and went back to return it two days later, because I was unhappy with the product. The product worked fine, but it didn't serve the purpose I thought it would serve. I didn't want to return it,I want to exchange for a better product. Baby City refused to honor the policy on their receipt. Which says goods can be returned within 7 days as long as its in its original shape. The product is in its original form, apart from the one day I used. This business has the worst return policy and customer policy I've ever experienced. ****a shops have better return policy. I'm not asking for my money back, I want to EXCHANGE and PAY MORE for a better product. Baby City's policy basically means, once you buy it, you are stuck with it, however unhappy you are with the product, once you pay for it, and open the product, its impossible to exchange or return it. ,Even if you do so within the 7 day grace period.