Worst experience ever!

I bought a bed last year from Sleepmasters, and the delivery took over a month, which I had to keep following up on. Now, a few months later, the mattress sinks in. I was told in-store to get my order details so that I can get a replacement. I made this order online, and suddenly, when I log onto my profile, my order doesn't appear in my previous orders. How am I expected to get a replacement? I sent an email over a week ago, and no one has responded to my email.