What the hell Amazon!

I ordered an item with Prime shipping on the 23rd and now Amazon is saying it is not going to arrive here until the 29?!!?!? WTF Plus the items was $2 cheaper via the seller who is sending it non-2day to me. This is not like a book, this is an item I desperately need and counted on arriving on the 25th. If I'd known it wasn't going to happen I'd have just gone to Target to buy it and skipped Amazon, or tried to put an order together at Diapers.com. This is so unacceptable.