I got a new Vodacom contract today (finally got my HTC One S! Yay!), and as I wanted to keep my prepaid number they did some magic to put that number on the contract. In the excitement, though, I forgot that I had a 100Mb data bundle that was only a few days old, and about R40 or so in prepaid credit - which is now gone Admittedly it's partly my fault for not asking what happens to that, but they didn't bother to mention that I'd lose everything either, so it's their fault too.
So if you're going to move from prepaid to contract, keep that in mind
Edit: Unless (grasping at straws) there's something I've missed? Some separate balance amount I should be checking?