Bad customer service!!!

Hi, I bought Roxanne full bed queen fabric for R8k from them. I called 2 months back even sent emails regarding the sagging/sinking mattress but no one seems to be interested, if I don’t follow up no one is saying any thing. Every time when I call they promise to call back and resolve the matter but they don’t. Please assist I need new mattress because it’s warranty is 8 years and I bought that bed in 2018 it’s only 2 years but am experiencing problems and bad customer service.