After sales service is the worst

We bought a mattress from Cloud Nine less then 10 months a ago and it seems to be sinking in the middle, we got a guy from cloud nine in to inspect it and as we though it had dipped pretty badly . The inspector had told us that " It was the worse he has seen". Of course you would then think it was easily replaced? NO! They asked us to pay extra for what we deemed as a manufacturers defect. Absolutely pathetic and not helpful at all.