Poor Service Delivery and Customer Care

I ordered (amongst other) an iRig HD2 from the takealot website.

I paid for the order (19 Nov 2018) and the initial delivery date was set at 28 Nov 2018.

Without any notice they moved the delivery date to 5 Dec and then 6 Dec.

Then takealot saif they are unable to deliver the iRig HD2 and that they will credit me the value to use on the site. I want to order the iRig HD2 from another site, so I want the money back - not only credit.

They are not responding to my request. How can they put up something for sale on their site and not have it in stock?