Cloud Nine Defects - no care attidute

I bought a Queen mattress (Cloud Nine Epic Comfort) from Beds Direct on 5th April 2018. Beds Direct were great. However, I complained to Cloud Nine that the mattress is already sagging after only a month. After them sending a representative to my house to "TEST" the bed I received the following communication from them "No visible defect was found". The flipping mattress has sagged on both sides and I am the only person sleeping on the mattress and I alternate one week at a time per side. This is totally unacceptable and this needs to be fixed. I guess Cloud Nine will wait until my Guarantee expire so that I have to part with more money.