Cannot access cellular data network after iPhone jailbreak and unlock to tmobile

So you've hacked your iPhone and unlocked it with TMobile. Good for you. Now you need data access. Here's how:

1.  go to settings>general>network>Cellular data network> APN
2. 1. note if cellular network does not appear and you have restarted phone
      since jailbreak, you may need to down load APN hack from cydia
3. enter ‘epc.tmobile.com’ for the APN value
4. browse away

 from http://www.crunchgear.com/2009/07/03/how-to-jailbreak-the-iphone-3gs/