Not happy about the bed quality and service I received from house & home highveld mall

I opened an account with House & Home at Highveld Mall six years ago and purchased a greencoil queen-size bed. I did settle and close my account after losing my job during COVID-19. I recently went to House & Home to report that the bed I purchased has an unexpected sagging in the middle. I'm referring to a bed that costed me R12,000. We had a break-in at our flat once, and as a result, I no longer have the slip. They told me they couldn't help since I’m no longer on their system how possible is that? Or they don’t want to assist. while I was there, one of their staff members said that I wasn't the first to voice my concerns about the bed. In this situation, what should one do?