Selling goods they don't stock and leaving me in the dark!!!! no updates!

I placed an order online for product "HK Junior Student Fold Up Desk - White (100 x 800 x 500mm)" and paid on the 15th of September 2020. The item is an online only promotion valid until the 5th of October 2020. My delivery update was that I will receive the order on the 17th of September 2020. On the date of delivery I received a call from a builders online agent telling me that there is a delay on my delivery but she will make contact with a new delivery date. On the 21st of September I called the builders support line for an update on the delivery of the item. After being transferred to a number of support agents nobody could give me any update. On the 22nd of September I called again. And same story nobody could assist. Then I received an email stating that the supplier is out of stock and that I will be informed of a new delivery date. Worst this is that the item is still for sale on the website no indication of stock levels!!!! It seems that builders warehouse will gladly take your money. I think they hope that I will just sit back and wait for the item. That isn't good enough I want what I paid for!!!!. You took my money now deliver the goods!!!