I didn't realise vodafone had changed their pre-paid cap plans to include data!
I'm on the $29 cap. Apparently they started to include data on the pre-paid caps starting from 9/9/2008.
I've got a 1st Gen iPhone and didn't realise my iPhone was using data until the weekend. I've used 2.7mb unknowingly since then - at 1c per 1kb, that's not cheap! Fortunately my iPhone switches to wireless when i'm at home and work.
I rang vodafone and they said they communicated the change via voice message when you call 1511 to top up your account. Who ever listens to that stuff anyway? I think they should have sent an SMS informing people to call 1511 for important changes to current pre-paid plans.
Ah well.