Poor Poor Quality Mattress

I bought a bed for my son at the Strubensvallei store in Dec 2014, for which I cannot seem to find contact details. This bed has totally collapsed right across the middle! For a bed that carries a 15 year warranty, this is unacceptable. I have sent numerous emails to all contacts that I can find on the web, have been assured by 2 of them that my problem will be escalated, but NOTHING TO DATE!! This is an ongoing problem for the last couple of months!! PLEASE HELP!!!!!!!!!!