I have tried this way and it works.
- Go into Setting on your iPhone
- select General
- select Network
- select EDGE on the bottom
You need fill the blank
Leave blank for Username and Password.
Then you may go back to Network and turn Wi-Fi off. Go back to main screen and select Safari to connect to internet or update Weather/Stock.
Reboot your iphone if it cannot connect ot internet.
PS. I am not sure the price charged by Vodafone, so be careful that.
Now update the price, Vodafone will charge AU$0.90 for every five minutes.