Over priced billing issue

I did an up grade last year May 2014. You receive 75 mins and 200mb data. I was told its like a top up. When its finish you need to top up. So when i used the call mins up and tried to call again it says you need to top up. So my bill has always been +-R200 since i'v taken it out. Well i let my son watch U Tube videos and thought that when the 200 mb is finish, well thats the end of the data. Well well well, to my surprise i see my bill is going to be R1300 just for data at the end of this month. When your data is finish it just continues but bills you at normal call rate and not data rate. This was not told to me when i took the contract out and now i must pay for something not explained to me. I want vodacom to get back to the recordings when i did the upgrade over the phone. I would like a credit then and a limit put in place, so this will not happen again.