There seems to be a bit of confusion, though, considering that some who had pre-ordered the Nokia Lumia 900 from AT&T had received the same email about the handset being out of stock, only to receive a subsequent message confirming the pre-order. You might want to call AT&T to confirm your order status if you have received the "out of stock" email.
As we already told you, new AT&T customers signing a two-year contract can get the model for free. The price on the carrier's website is $99.99 with a signed 2-year contract. If you are already an AT&T customer, your best bet might be to turn to Walmart for the Nokia Lumia 900. The deep discounter is offering the model to both new and existing AT&T customers for $49.99 with a signed contract, a 50% discount from AT&T's price.
If the pre-order inventory of the Nokia Lumia 900 is indeed sold-out, it might have some implications for how readily available the device will be after it's launch next Sunday.
source: AT&T via WMPoweruser