Lewis store Cradock worst experience ever

Bought a bed at lewis store in cradock explained to Dean the lady that helped me that i wanted a hard matress that can take up to 160kg on each side. She the showed me two mattresses and we decided on the more firmer one. 4 days after i bought the bed the matress started sagging i called them with my complaint and they informed me that the matress i bougjt can only take up to 100kg both sides so i myself weigh 96 kg my side as weel as my husbands side who are 135kg both saged by 2.5 cm where the manufacturer informed me they wont replace my matress as it is normal for matress to sag within 4 days. So i followed up with the atore in cradock they told me to follow up with head office. I did so and they told me to follow up again as they are still working on a solution so now it has been 2 weeks later i have called the store numerous times and they still have not replaced my matress. This is the worst service ever. My complaint was well before the 7 days were up. Thwy are quick to take your money but dont want any responsibility when they ***** up