mattress sagging

We bought a queen size Sealy Promo Jasmine mattress and base on 14/2/2009 and masterguard application for stains. The mattress has been sagging for some time and we have been experiencing back and hip pains. We phoned and they sent an inspector around and he took photo's and reported back to Customer Care Department. <br> Christine phoned and informed me that the guarantee expired Feb 2010 but the warranty expires in 9 years which is 2018. In order for them to replace the mattress which is now discontinued we need to pay R3224.01 and recovery fee of R790.02 for the stain on the mattress. Needless to say should we agree on a replacement they do not take the old mattress away as it has a stain but we still need to pay the R790.02. We told them that we would not buy another mattress from them and that we wanted to speak to the supervisor. Christine then phoned me back and said that they will charge us R2015.01 and R790.02. We would like to know what is the warranty for and what does it cover. We thought a Seally mattress is one of the best but how wrong we are.