Amazon Late deliveries

I have Amazon Prime so i pay a little each month in expectation of prompt Amazon service regarding my delivery. I foolishly thought when I ordered something on Amazon that I would get fast and prompt delivery. No so this time because people advertise items they don’t have or don’t have in stock. They are independent sellers and nothing against that but I’m figuring if you are going to represent Amazon Prime you should be able to fulfill orders and delivery. I never thought Amazon Prime would take over a week. (Still haven’t got it). I thought free fast shipping was one of the benefits?