If you are connected to an AT&T cell phone via a USB cable, you can use wvdial to access the Internet. Edit the /etc/wvdial.conf file to look like the following:

[Dialer Defaults]
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
Modem Type = USB Modem
Baud = 460800
Stupid Mode = 1
New PPPD = yes
Modem = /dev/ttyACM0
ISDN = 0
Phone = *99#
Password = CINGULAR1
Username = WAP@CINGULARGPRS.COM


Then, just start up wvdial to connect to the Internet!