Overpriced sealy faulty mattresses

I bought a sealy bed from Dial-a-bed on Somerset, Cape Town on 07/10/2023, a sealy skyline extra firm mattress. Last year we started noticing that the mattress is sagging and dipping in the middle.

We reported this issue to Dail-a-bed and someone from sealy did come over my place to inspect the mattress and now we just got a report that the mattress has no defects when the mattress is actually not good and still under warranty. We spent the money we spent on this mattress because we believed in sealy as a brand and we assumed that the mattress was going to be good quality based on the amount and the brand name. Now we are stuck with a terrible mattress and it seems like no one wants to take responsibility.

Is there anything that can be done to fix this problem or I am just stuck with a bad mattress that did not even last a year?