Did you find a way to make card work? Did you find the card on a port?
In Kubuntu, I can install Sierra AC875 and connect faster than ATT communication manager can install in XP.
What I did was find phone #, network name & modem name in ATT communication manager, then configure kppp same. UID and PWD can be any characters in ATT system, Alltel may be different but Alltel uses same towers as Sprint & VZW so I suppose authentication is same.