RUDE SERVICE AND EXTRA DATA CHARGES

I've upgraded my line to a promo VODACOM Is running 30GB day 30GB night plus 30GB anytime and 10GB video ticket.. It worked 100% up until last month then they said they where going to charge me R1800 for the 30GB anytime data I called an was very rudely told that I added it so I'll pay for it few days later I was called again and explained that it's promotional data and would not be paying and that if it was added to my account it would be credited immediately and it would not affect me now I called in and was told that I need to go back to the shop where I did the upgraded!!? Then after arguing about that for a few minutes a credit was requested and was told I'm Still going to pay the full amount this month but next month I will be credited!!! I WILL NOT ACCEPT THIS !!! THIS WAS NOT MY AGREEMENT WITH VODACOM!!!!