Ok, you're a corporate BB user. You didn't mention that. You need the WAP only version of PocketDay. Delete the current version (you must do this first). Then install:
http://www.crossriversystems.com/files/v40/pdp-wap.jad
Select AT&T from the pocketday communications screen and you should be ok. Weather probably won't work as the AT&T apn is so old it eats characters. I would get off Blue and get onto Orange. Then you can just switch comm settings to Cingular.