Both my partner and I both have the 3g 2nd gen Iphones.
we did not get iphone data plan as we do most with wifi and some $1 data.
we both used the $1 per 10mb per day by changing the data settings to
www.vodafone.net.nz and it worked.
Just a simple deleting the iphone part of the settings and you can use the $1 per day data.
But we found that sometimes when we changed the settings back so that data was disabled we
would still be recieving the data ie emails to our iphones. We could even surf the net with the wrong settings
we even changed the settings to stupid words, nothing to do with vodafone or iphones. still we were able to
surf the net or receive emails.
we had a little panic as we saw mega $$$ being wasted on this fault.
we turned off the iphone the restarted it no change.
then we turned it off, changed our sim for another one, we used prepaid as one was handy,
then restarted the phone,
Thank God there was no data being received .

we are not sure what happened, we think the settings froze and just wouldnt change back even tho we had
change them back in text, but the phone did not see this.

so if you are having troube like this try to start your iphone with someone elses sim.

worked for us several times.

hope this helps someone out there.

and ps roll on mms, landscape keyboard, copy and paste .