Misleading customers

I recently was over charged on data and after spending hours on the phone i was told that i will get a discount for the data that was charged and received a very nice email with a full breakdown of how much i will be charged only to find out that Vodacom charged me the full amount, i called and asked what has happened and why i was charged the full amount over R600 only for data they asked me for proof that someone said that i would pay a discounted rate, Really cant you see on system as the email cam from your system stating this, I am now waiting over 2 weeks for feedback and still no help, i pay Vodacom more than R1300 a month and to be treated like this is so wrong . please can someone fix this