One of the features I missed when I switched over to the iPhone from Windows Mobile is the ability to use the phone as a modem. This is called tethering in the Apple circles. Apparently, the 3 and Vodafone networks have enabled this on their ipHones, but Telstra has yet to come to the party.
There is a way to enable this on your iPhone without a Jailbreak.
First, determine whether you are using the telstra.internet or telstra.iph APN (access point for the Carrier).
To do this, browse to Settings, General, Network, Cellular Data Network and view the APN setting.
Then, on the iPhone Safari Browser, got to one of the following links.
http://weave.zarack.com/TelstraTetherv1IPH.mobileconfig – for the telstra.iph APN
http://weave.zarack.com/TelstraTetherv1Internet.mobileconfig – for the telstra.internet APN
You will be asked to install a Profile called Enable Tethering.
After it is installed, browse back to Settings, General, Network and there will be a new item called Internet Tethering, This can now be turned on or off as required.