Difficulty level:
Medium

What you need:

>Mac OS X 10.5 or later

>Download this carrier settings file from gizmodo.com and double-click it to mount it in Finder

>iPhone OS 3.0 (7A341) Gold Master final release for iPhone (see below note)

>First prerelease version of iTunes 8.2 (download link)

>Final release version of iTunes 8.2 (download link)

Next, quit iTunes and enter the following command in terminal:

defaults write com.apple.iTunes carrier-testing -bool TRUE

Contrary to many articles, you don’t need to install a pre-release version of iTunes.

When you restart iTunes, connect your iPhone and you’ll be able to option-click the Restore button to choose the .ipcc file in that disk image. Rather than doing a full restore of your iPhone, it will simply update the carrier settings. If the update is successful, the Network page under general settings will show an Internet Tethering option.