Below these instructions is a list of APN settings for various service providers located in the USA.

In your Cell Phone's Options (Where you configure your Cell Phone) find TCP.
In TCP you will find the following Settings:
APN:
Username for APN:
Password for APN:
Instructions:
Enter and Save the appropriate settings for your provider in your cell phone, and test them to see if your application begins to function. When your application begins to function, you have found the correct settings for your phones provider. More settings may be found by searching the internet.

Carrier: Cingular/ATT
APN: wap.cingular
UserName: wap.cingulargprs.com  or  WAP.CINGULARGPRS.COM
PassWord: cingular1  or  CINGULAR1  (Password may need to be capitol even with all other settings lower case)

Carrier: Cingular/ATT
APN: isp.cingular
UserName: ISPDA@CINGULARGPRS.COM
PassWord: CINGULAR1

Carrier: Cingular/ATT
APN: isp.cingular
UserName: (Blank)
PassWord: (Blank)
Yes UserName and PassWord are left Blank

Carrier: Cingular/ATT
APN: wap.cingular
UserName: (Blank)
PassWord: (Blank)
Yes UserName and PassWord are left Blank

Carrier: Cingular/ATT
APN: blackberry.net
UserName: (Blank)
PassWord: (Blank)
Yes UserName and PassWord are left Blank

Carrier: Cingular Blue
APN: proxy
UserName: (Blank)
PassWord: (Blank)
Yes UserName and PassWord are left Blank

Carrier: AT&T
APN: PDPWAP1 or pdpwap1
UserName: (Blank)
PassWord: (Blank)
Yes UserName and PassWord are left Blank

AT&T
Gateway IP: 10.250.250.250
Port: 9201
APN: proxy

Cingular
Gateway IP: 66.209.11.61
Port: 9203
APN: blackberry.net

Carrier: Nextel
APN: internet.com
UserName: (Blank)
PassWord: (Blank)
Yes UserName and PassWord are left Blank

Carrier: Sprint
APN: No Configuration Needed
UserName: No Configuration Needed
PassWord: No Configuration Needed

Carrier: T-Mobile (Verified good APN - their 3G network)
APN: epo.tmobile.com
UserName: (Blank)
PassWord: (Blank)
Yes UserName and PassWord are left Blank

Carrier: T-Mobile (Verified good APN)
APN: wap.voicestream.com
UserName: (Blank)
PassWord: (Blank)
Yes UserName and PassWord are left Blank

Carrier: T-Mobile (Verified good APN)
APN: internet2.voicestream.com
UserName: (Blank)
PassWord: (Blank)
Yes UserName and PassWord are left Blank

Carrier: T-Mobile
APN: internet3.voicestream.com
UserName: (Blank)
PassWord: (Blank)
Yes UserName and PassWord are left Blank

Carrier:T-Mobile/T-Zone (USA)
APN:wap.voicestream.com
User name: TMobile.com 1234567890     (where 1234567890 represents YOUR 10 digit mobile phone number)
Password: (Blank)   (or your T-Mobile password - but typically left blank)

T-Mobile (US)
Gateway IP: 216.155.165.50
Port: 9201
APN: wap.voicestream.com

Carrier: Verizon
APN: No Configuration Needed
UserName: No Configuration Needed
PassWord: No Configuration Needed
WAP Gateway IP: 153.114.115.100
WAP GateWay Port: 9203

Verizon
Gateway IP: 153.114.115.100
Port 9203

Verizon Alternate
Gateway IP: 12.168.70.74
Port: 9201