I had the same problem with my phone. I spoke to a tmobile representative and she was able to walk me through the setup.
1. Setting > Connectivity > Network Profiles > Create
2. Set Name > T-Mobile
3. Access Name > epc.tmobile.com
4. Auth Type > None
5. Home URL. >
http://wap.t-zones.com6. Linger Time 300
7. Advanced Setttings > All boxes must be unchecked.
8. Save Changes
Next we need to create a profile for the messaging.
1. Setting > Connectivity > Network Profiles > Create
2. Set Name > T-Mobile MMS
3. Access Name > epc.tmobile.com
4. Auth Type > None
5. Home URL. >
http://mms.msg.eng.tmobile.com/wapenc6. Linger Time > 300
7. Advanced Settings > All boxes must be unchecked.
8. Save Changes
Next we need to make sure the network settings is set to manaul.
1. Setting > Connectivity > Network Selection > Manual
2. Save
Now we have to point the browser to the correct Profile we just created.
1. Next Click on the Browser to Open.
2. Click on Browser Settings
3. Click on Browser Profiles
4. Make sure TMobile is highlighted not TMobile MMS
And that should be it. Your phone should be able to work on a TMobile Line.