1. Go to Home screen
2. Navigate to Settings
3.Tap General, then tap Network.
4.Turn Data Roaming On -- this will allow your iPhone to locate T-Mobile’s data network.
5.If you see a setting for 3G, turn it Off -- the iPhone cannot currently connect to T-Mobile’s 3G network, and this setting will interfere with its attempt to connect to the EDGE network for service.
6.Tap Cellular Data Network
7.In the APN field, enter either epc.tmobile.com (or internet2.voicestream.com if that doesn't work) -- this tells T-Mobile which version of their Internet network you want to connect to.
8.Leave the Username and Password fields blank -- T-Mobile will assign this information based on your SIM card information.
9.Return to the Main Menu and open Safari to browse the Internet.
MMS Settings
1.Go to Home screen.
2.Tap Settings.
3.Tap General.
4.Tap Network.
5.Tap Cellular Data Network.
6.Enter the following information under the MMS section.
a. Enter wap.voicestream.com into the APN field. Backup setting: epc.tmobile.com
b. Leave the Username field blank.
c. Leave the Password field blank.
d. Enter 216.155.174.84/servlets/mms into the MMSC field
e. Enter 216.155.165.50:8080 into the MMS Proxy field.
f. Leave the MMS Max Message Size field blank.
g. Leave the MMS UA Prof URL field blank.
7. Press the Home button to return to the main screen of the phone.
8.Turn the phone off and back on to put the settings into effect.
9.You should now be able to send/receive Picture Messages.
Alternate MMS setup (if first way doesn’t work):
1.Go to the Home screen.
2.Tap Settings.
3.Tap General.
4.Tap Network.
5.Tap Cellular Data Network.
6.Enter the following information under the MMS section.
a. Enter epc.tmobile.com into the APN field.
b. Leave the Username field blank.
c. Leave the Password field blank.
d. Enter mms.msg.eng.t-mobile.com/mms/wapenc
e. Leave the MMS Proxy field blank
f. Leave the MMS Max Message Size field blank.
g. Leave the MMS UA Prof URL field blank.
7. Press the Home button to return to the main screen of the phone.
8. Turn the phone off and back on to put the settings into effect.
9. You should now be able to send/receive Picture Messages.