I might have to complain as well, ordered something yesterday at about 3pm which said it would be delivered today. The order is showing in my account as to be delivered today and also awaiting despatch. The two other things I ordered a couple of hours earlier have both arrived though.
This is after an order from the start of the week came a day late and they gave me an extra free month of prime. Should I try for a second free month?
Yes you should. They will no doubt give you another month.