Here's the settings I have on my phone and it's been working fine for almost a year now. Good luck!
Name : net10
APN:att.mvon
Proxy : not set
Port: 80
MMSC: http://mmsc.cingular.com
MMS Proxy: 66.209.11.33
MMS Port: 80
MMC:310
MNC:410
APN Protocol IPv4