You could potentially sue them (and possibly the furniture's manufacturer) for product liability, if the sofa is unsafe; for breach of contract, for not providing what you are paying for (a safe-to-use sofa and chair); and/or negligence (for carelessly doing something making the sofa and chair unsafe, like dousing it with some chemical). In the process, you could seek monetary compensation (e.g. for any medical bills; to recover the amounts you paid for a sofa you can't safely use) and/or to get out of the contract (to rescind it) and get your money back. If they will not voluntarily work with you, your option to force them to do so would be a lawsuit; though it's quite possibly that if you do file a suit, at that point, they will choose to settle rather than go to court. You could try suing in small claims court, acting as your own lawyer, if the amount of money (cost of the furniture) does not justify hiring an attorney.