Here's a little guide that allows you to enable tethering on the iPhone 3G and 3GS with firmware 3.1.2. We use a hack that changes the CommCenter and eliminates the need for a digital signature for the appointing authority dedicated to the navigation on the computer, so it should be possible to reset the right data for Vodafone Pack

1. First run Cydia and search for "iphone-notes. Install this repository and return to the tab "Search".

2. Now look for "tethering 3G - 3.1.2" or "tethering 3GS - 3.1.2" depending on the model of your device and install the package.

3. Restart the iPhone and then connect to the site www.unlockit.co.nz directly on the iPhone to create a custom APN. Enter all data necessary for the connection, after you create and install the profile.

After you restart you should see the field "tethering" in the settings (if it had been disabled by the update to firmware 3.1.2), and also you should be able to sail with the appointing authority desired.