Damaged Couches 2nd time around

I am fed up and mad as hell with Lewis stores. We bought couches at Lewis West Street Durban about a year ago in CASH. After 4 months 2 of the 3 couches broke. It took us a further 3 months for their people to come out and fix the couches. They only came to collect after numerous calls, store visits and calling the Lewis head office. Then 3 months down the line the foam of the couches are sinking in and we are now sitting on planks. SO here is the situation... I demand new couches and we will not pay for it. How can you expect to sell couches for R6000 when it only lasts less than 1 year? Please someone from head office call me so we can sort this out. I am NEVER buying ANYTHING from you as you only sell damaged goods!! sorry you lost me..