Warranty claim rejected - apparently WE SLEEP WRONG

I bought a Serta bed at Sleep masters in November 2023. After 4 months the top part of the matrass started pulling on each end. The one end toppled over the matrass end and the other end was pulling inwards. I laid a complaint by Sleep masters, and they logged a warranty claim. Serta contacted me and I sent them everything including pictures. The consultant was rude, and the claim was rejected - the reason: WE SLEEP WRONG. I also told them we don't use the bed as a couch (that is want living rooms are for). But according to them it's our fault (after 4 months of having the bed). I weigh 56kg and my husband about 65kg, so we are not heavy people.

I had to buy a new bed (I went with a Sealy) that at the end was way more worth it. Money well spent. It was double the Serta price. I will not make that mistake again.

We moved the Serta bed into my 14-year-old sons' room after we bought the Sealy. He weighs about 45kg. When I made the bed today, I saw that the matrass now even looks worse!! How is this possible with someone that weighs 45kg sleeps on the bed. Does he also SLEEP WRONG??