Sorry that you're going through that. I personally have been with ATT since 1995, back when it was Bell South Mobility, then Cingular, etc. To tell you the truth, I've never had a good CS experience with them, if I could change I probably would. But the area that we live in ATT has the best signal (mountain region), so I really have no choice.
I ordered to new iphones on 10.21.11, I was told the same 21-28 days. Somehow, I was lucky and they notified me only 10 days later via email and tracking # that they were being shipped, they arrived the next day via FedEx overnight.
I would stay on the phone, be persistant, polite yet firm and you can get to the "right" person to make it happen. Your order probably fell through the cracks and shoved to the back burner.