Have bought a mattress online last october, super king size 6ft, the mattress was 2.5 inches short of the 6ft specified, after much persistance they agreed to change the mattress for another one as they suggested that it might be faulty, so we recieved another one in November and were told that it would grow, but 8 weeks later the mattress is still smaller than the base of the bed and we seem to be getting nowhere at the moment, what other steps can we take?