OMG FINALLY!!!! IT WORKED!!! wow FINALLY i was on a binge for like 2 days figuring this out.. heres what I did
Installed Motorola USB driver (*supplied on cd, or website here HERE )
created a Dial up connection through windows (XP sp2)
phone number = *99#
username: WAP@CINGULARGPRS.COM
password: CINGULAR1
Next go to Control Panel>
Phone and Modems>
click on Motorola USB ... >
Properties > Advanced tab >
type +CGDCONT=1,"IP","apn_name" (*Replacing apn_name with your APN like WAP.CINGULAR <<NOTICE THE UPPERCASE!)
DONE try to connect.. worked for me! (mpx220 cingular CA w/laptop XP sp2)
############ GPRS Settings for your Phones ###########
You dont need to set any of this if your GPRS already works on your phone. This is only reference for those who forget settings or have phones setup w/different carriers than provider currently on phone.
Cingular GPRS Setup on MPx220 ----------------------
GPRS settings:
Hit WebAccess
Hit Web Sessions
Hit Menu and New
Change as follows:
Name: Cingular GPRS
Homepage: http://device.home
Service Type 1: WAP (capital letters)
Gateway IP 1: 66.209.11.61
Port 1: 9201
Domain 1: Blank
Service Type 2: WAP (capital letters)
Gateway IP 2: all zeros
Port 2: 9201
Domain 2: Blank
DNS 1: All zeros
DNS 2: All zeros
Timeout: 15 minutes
CSD No 1: 14152441012
Username: WAP@CINGULAR.COM (must be in all caps)
Password: CINGULAR1 (again all caps)
Speed (BPS): 9600
Line type 1: ISDN
Csd no 2: Blank
Username 2: Blank
Password 2: Blank
Speed (Bps): 9600
Line type2: ISDN
Gprs apn: wap.cingular (all lower case)
username: WAP@CINGULARGPRS.COM (all upper case)
Password: CINGULAR1 (all caps)
Click in DONE
After this, you will be able to see the name "Cingular GPRS" listed on Web
Session. Highlight that name and click on the middle button. Select "Set
Default" and press select.
MMS Settings:
Hit Menu
Select Messages
Hit Menu (middle button) on Create Message
Select Message Setup
Hit Change on MMS Message Setup
Select Server Info
Hit Menu (middle button) on a selected profile
Select New
Change as follows:
Service Name: Cingular MMS
Server Name: http://mmsc.cingular.com
Web Session Name: Cingular GPRS (Hit change, choose and select "Cingular
GPRS")
Click in Done
ATT Wireless -------------------------------
ATTWS
I found this on another board:

Step 2: WAP/GPRS Settings
2: Set Homepage URL to http://home
3: Set Security to Non-Secure
4: Set Bearer to GPRS
5: Set IP Address to 010.250.250.250
6/7: Make sure username and password are blank
8: Set APN to 'proxy' without the ' marks
Step 3: MMS Settings
2: Set Connection URL to http://mmsc.mobile.attwireless.net/
3: Set Security to Non-Secure
4: Set IP Address to 010.250.250.100
5/6: Make sure username and password are blank
7: Set APN to Proxy (note capital P)