This simple service is being provided by BenM.at. A big thanks to them for putting this together.
Press to launch Safari from your iPhone SpringBoard.
Navigate to http://help.benm.at/help.php.
Press the Mobileconfigs download button
Press to select your country from the list
Press to select your carrier from the list that appears.
An Install Profile window will appear. Tap the Install button.
You will be warned that installing this profile will change the settings on your iPhone. Press the Install Now button.
Once the profile has installed successfully press the Done button at the top right of the screen.
Reboot your iPhone then press to launch Settings from your SpringBoard.
Next select the General Menu.
Press to select Network from the General Settings.
Select Internet Tethering from the Network Settings.
Move the Internet Tethering switch to the ON position.