I recently changed Vodafone packages. I noticed after the change over they had dropped all of my carry over minutes (around 150).
I rang Vodafone and they informed me that switching from a Legacy package (from 2003) to one of their newer ones does this and nothing can be done to reclaim the lost minutes.
What do the relevant terms & conditions of the various contracts that you signed up to say? Perhaps it was not a rip-off but something that you simply didn't apprise yourself of by reading these?