Bad quality mattress

After using a R9000.00 Dynamic Te****utic mattress for 6 years it started to form a hollow bodyform on both sides with a little hump in the middel. This is supposed to be a firm mattress. It is soft and not comfortable anymore. After I sent an e mail to complain, I was told that it is normal for a firm mattress to do this. Seriously! I will never waste my money on this make and will not recommend it to anybody. A very unhappy customer