Beware of scam

I ordered a spare part from these guys in Durban. Received the invoice, paid with immediate clearance as was requested and they told me they had couriered the part to me the same day. Since then they have refused to provide me with a tracking number so I believe that I have been scammed - they've taken my money and there is no part on its way. If it was couriered why have they not asked me for payment of the courier costs?