I find I can fix this easily by calling my credit card company.
Ordered by telephone and was told computer would be delivered in 48 hours. As it turns out, there were none in stock, and none of their sales knows when it will come. Each time I call they say "it is about to be shipped" but weeks have passed and nothing has arrived. I have tried to cancel the order four times now, and have been told I will get a refund shortly on every occasion. But those are all lies. They just keep the order open, won't refund my money, and speak nicely on the phone when I call.