Sagging king size Bed!!!!!!!!

Hi, At the end of 2015 I bought a Sealy pillow top king size extra lenght matters. What the store at the time claimed was one of the best mattress, barely a year later the matters was sagging horribly, they replaced it with no complaint but just over a year after that I find myself in the exact same situation.

First they wanted me to pay a service fee of R1000.00 as aparently it is not longer under garantee but still under warrantee which I refused to pay and had to fight them to waver. They then a agreed to replace the matters and on email sujested I go with a higher range of thier product, which House and Home claims they don't sell. So i demanded that they Either refund me or provide me with a new garantee which the store claims they have refused to as they do not reply to any of my emails anymore.

I use to belive that Sealy was the best on the market this is why i payed so much for the bed i bought, but this no longer seems to be the case.