Squicky mattress

I Bought a double bed last year around September, early this year the mattress started to make noise and springs hurting and you could hear all the tossing and turnings. I took back the mattress aND they changed it for me. After 4 months of using the mattress the same issue started. Now am expected to pay R2000 for them to change my mattress and they will take my mattress and give me a new only if I pay R2000 while am paying for the mattress and is still under warranty