Restonic refusing to exchange my mattress

I bought a bed in 2017 may at ok furnitures in 2018 I experienced problems with mattress caving in and making squeeky sounds they changed the mattress now in 2019 the same problem again now I have 3 months since I have put the claim at ok furnitures store untill I asked for the email and I emailed the guy from Restonic by the name of Ryno and i sent him pictures of the Mattress that lost its colour or the fabric that is infused on top and insisted on saying the mattress is dirty and of which it is not I had waterproof mattress protector on it and he promised to come exermine the mattress for a month and eventually came now he saw it himself that those were not stains but the fabric lost colour and I even reminded him that the first mattress had the same problem and he approved the change he then took pictures of the mattress springs also popping out on the sides of the mattress he then said to me they say they will not replace the mattress because there was steins on the mattress of which he saw it with his own eyes that the mattress was clean now I feel m struggling to be helped because I no longer owe them I was supposed to finish the bed this year December and but I got it paid up in February this year I feel I am suffering a loss because of the factory faults and materials which is not of quality please assist

Thank you Regards Mosala ***