undelivered online orders

I am writing this, as i am not happy with the service i have received from builders.

On the 30/05 i purchased a hyper tough 120A mig welder online as builders Centurion did not have any in stock. After ordering online, the delivery date was to be on the 04/06, on the 04/06 the afternoon i followed up, and was advised that it was being sent from Builders Gezina, however they did not have any stock, but they do have a display(demo) unit, without asking for any discount or refund, I advised that they can send the display unit, as I just want what I ordered. I was then promised high and low with e-mail confirmation that I would have my item on Saturday. Well needless to say, it is not Monday 08/06 and I still have not received my item.