Go buy a t mobile Sim..pop it in. Go to settings>mobile networks>preferred network..choose GSM. Then after that you should be able to edit your apns in access points names.
Should be pretty easy
Just don't go flashing any T-Mobile Roms
I have tried this method already.
First off there is no option for "preferred network" also when I select GSM theres an option for "Manual" or Automatic" I guess it should be on Automatic?
What I used earlier (which did nothing after I restarted the phone) was:
Settings>More Settings>Mobil Networks>Access Point Names>
Than I pressed the plus sign and configured it this way:
Name: T-Mobil
APN: fast.t-mobil.com
Proxy: 216.115.165.050
Port: 8080
Username: Not Set
Password: Not Set
Server: Not Set
MMSC: http//mms.msg.eng.t-mobil.com/mms/wapenc
Multimedia message proxy: 216.155.165.050
Multimedia message port: 8080
MMC: 310
MNC: 260
Authentication type: Not Set
APN type: Not Set
APN protocol: IPv4
APN roaming protocol: IPv4
Turn APN on/off:: (Shaded grey) Checked
Bearer: eHRPD
Mobil virtual network operator type: None
Mobil virtual network operator val..: (shaded grey) Not Set.
This never worked.
Edit/ PS: And yes my T-Mobil Sim is in the phone.