Sinking couch and broken arm rest

I bought a couch and it sank within 2 month and the arm rest broke, I went to the shop to report it and they sent me away and said I must report it on. I did and did not get help until 6 months later after the fourth attempt they responded and said they can't replace it but will fix the one. I told them that the couch sank within 2 month which shows a factory fault and I reported it immediately but they were not willing to assist. I don't want any of their furniture anymore I just want my money back.