Faulty Bed

In 2012 we bought a king koil bed at furniture city in fourways, within a year the bed was damaged, it looks like a ship with this huge dip in the middle and as u turn there are all sorts of sounds. The bed is worn out. Looks like a bed weve had for years. We are not big people to have a bed sinking like that within just 3 years is not right. When we took this up woth furniture city they kept pushing us from pillar to post until the shop closed down. Someone please help as i can not handle these back aches anymore.