Morulebg Mall Fairprice sold me what they don't have and I want what I paid for

I bought a Headboard on the 1st May at Fair price Moruleng Mall and now I am told that they do not have stock but only the one on display.This means they are selling things that they do not have ,now I have to wait ,this is wrong . Why do they have to sell something they don't have in stock. I want what I paid for or they should take back the matching couch I bought and give me back my money for both items because I believe they deceived me into buying this couch knowing very well that they will say i have used it and knowing vwry well that they do not have stock for the matching Headboard.