Serta Bed is the worst bed i have ever owned!

I purchased a SERTA king sized bed with a so called 12 year warranty and 2 year guarantee (at \House and Home"in North West Province). I noticed on the first night slight sagging in the position I sleep with a hard ridge in the middle of the bed. This becomes extremely uncomfortable after 2 to 3 hours of sleep and results in back pain and little sleep from the early hours of each morning. I called \""House and Home\"" and they got the SERTA rep out to inspect. Upon inspection she agreed with me about the sagging and the excessive hardness in the middle of the bed and wrote this in her report. The next day I was informed that SERTA feel this is a comfort issue which they are not going to do anything about. Before the rep even came out she tried to pass the buck and told me I should rather try get House and Home to swop the bed with their 7 day comfort exchange policy. I was informed that they only meet their guarantee obligation if there is 3 to 4 centimetres of sagging. REALLY!!! Maybe after 50 years a bed might eventually get up to 4 centimetres of sagging? A new bed should have NO sagging! Model of the story - PLEASE DON'T WASTE YOUR MONEY ON A SERTA BED LIKE I DID!"""