Vodafone called back yesterday.
I can move to a plan that would cost me $10-$20 per month more and get a (more or less) free phone. Alternatively, I can stay on my current plan and pay $379 (ex GST) for the same phone.
In both cases I would need to sign up for another 2 years (which is fair enough).
Excuse me for being a cynic, but it's either "pay more over time" or "pay more now".
I turned them down. I've got 5 months left on my plan commitment, after which I can move to another provider with no penalties. Now that sounds more interesting.