Poor response to query and seemingly ineffective stock management by such a large retailer

I made a purchase online to make use of one of the black Friday specials offering 3 pairs of children's shoes for the price of 2. When the shoes were delivered, only 2 pairs arrived. I logged a query on the website around the third pair of shoes on 13 December 2021 and received no reply or response. I proceeded to call customer service on 28 December to find out why I had not received the third pair and why I had not received a response to the query logged.

The answer from the consultant was as follows: 1) There was no stock of the third pair when my order was assembled. This is despite the fact that I was able to finalise the order successfully on my side, as the shoes were in-stock per the system. According to the consultant, when online orders are made, even if there is stock, the stock is not allocated against the order and at some point ran out. Isn't that ridiculous? Surely Woolworths has a real time stock management system to allocate stock to orders so that this does not happen? 2) When I asked why I was not informed about the shoes not being in stock, the answer was that an email should have been sent but it could go to the spam folder. I received no such mail. If it was in spam it probably got auto deleted. 3) When I asked if I could get another pair of same value/size as the pair not delivered, the answer was no because the order has been concluded. I find this totally unacceptable and unhelpful. The order was made when a special was running and I did not get the goods promised.