Poor service

Hi I bought a sealy Colombia mattress and base set on 27th August 2024. Same day I slept on the bed, the mattress started sagging. I complained and the mattress was exchanged but the same mattress they exchanged was sagging again within a week. I logged a complaint again and they told me they were going to exchange again,this was in November 2024 and in January they told me they closed the complaint as it was resolved but I never received any matress exchange. I logged another complaint like they told me to and nothing is happening,I’m stuck with a sagging matress calling customer care everyday, I don’t know what to do anymore