This is intentional
We had EXACTLY the same issue with a discounted Galaxy S7 Edge a couple of years ago. System showed it as in stock, placed the order then heard nothing.
After repeated emails and calls they admitted the system couldn't handle all the orders and would we like something else?
Took 10 days to get a refund.
Now the cynic in me adds up all the interest from the orders placed but not fulfilled and that's a lot of money. Not to mention all the premium rate calls on their "special" number for customer service.
If it was a genuine system fault it should be well fixed by now.