Restinoc beds are sagging

I bought a Restinoc bed at one of the retailer's in December 2015, and started using it in April 2016 when I got to my new house. In July 2017 the bed was sagging in the middle. In November 2017, I consulted the Dr as I was having backaches. I went to the retail shop to file a complaint on the very same month since the bed was still under warranty. In January 2018, Restinoc sent their consultant to assess the bed. That consultant assessed the bed and told me that I should have turned the bed on monthly basis and therefore handed me with the instruction manual of which I never got initially. He further told me that the bed was having my body impressions and they will only change the mattress not the base. In March 2018, I called the call centre to enquire about my complaint and the consultant on the phone told me that my complaint was dismissed. Everytime I look into that caving bed, that brought me backaches and waist pains, I worry that I should have used my R6000 for something of value than throwing it in a drainage. Frustrated and angry @ Lakeside, Vaal.