回複：us mattress

First, check what the receipt and what the warranty said? What will you do if you are not satisfied? Did the mattress sink because of bad quality? Second, if the store really does not have a return policy, you will have to resort to your local consumer protection law, which you may get on the state goverment's website. Be certain of your words, damage is not a term for quality. The mattress may sink due to its quality below what the factory warranted and you may get a relief under the warranty agreement accompanied with the product. If you are not sure, consult a local attorney or some consumer protection organizations.