Defective products sold to customers

We bought a Sertapedic double bed via House and Home which started sagging after a few years and worst is it has barely been used as it is at our holiday home which we use only twice a year. It took weeks for Lylax to send a representative to inspect the bed, first they pretended not to have received my emails yet they provided the email address to me. After several calls they finally responded. Upon inspection it was found that the main supporting pole in the base broke that's why the mattress started sagging. The piece of wood has a defect which clearly was not identified during the quality assurance process. Now Lylax wants to charge me to fix their inferior product completely ignoring the fact that they sold a defective bed to me, under the pretense that it is a quality product. When I challenged them on the poor quality they suddenly seem to have lost my email address again. I have requested several times to escalate the issue to Senior level but sad to say no success so far.