Wrong product delivered. Still being held liable

Ordered a Lenovo Thinkpad Edge from the FNB Smart Device page.<br> They delivered a Leonvo E50.<br> Document that I signed for stated the Thinkpad Edge was in the box.<br> Contacted the call centre to inform them the wrong device was delivered.<br> Some person on the phone tried to \sell"me on the fact that the E50 was a better product than the Thinkpad Edge (which it is not: the hard drive's rpm is 5400 versus 7200rpm on the Thinkpad Edge. A distinct difference in performance).<br> Then told that they don't have stock of the Thinkpad Edge anymore.<br> Obvious question: Why wasn't I informed that they don't have stock and would be shipping a different product? (I ordered and want the Thinkpad Edge"