Concerned consumer on faulty online store.

I bought a shoe online that was one of the higher end brands at Woolworths. The next day I received an email informing me that the shoe was out of stock in the size I had wanted. When I checked again on their online store the shoe was back available in another size that was not available on my initial purchase. I am so concerned that there maybe a system fault issue going on as the sizes available just keep changing daily on their online store.

As I have mentioned that this is one of the higher end brands available at woolworths and the shoe is now priced at 50% off from the initial price... I am so disappointed with this system fault, could woolies please fix it. You can contact me for the product item code.