R8500 in Data usage charges

I have recently upgraded my data line to a voice line and specifically requested a voice line that is TOP UP. When I saw my bill and realised that there's so much data charges, I contacted Vodacom and was told that the person who did my contract upgrade did not explain to me properly and that they're not liable as it was a face to face situation. I then logged a service call and the next day I received a call from someone said they were willing to bring the bill down to R1099.00 and that that's all they can do for me. I kept querying how they could give a limited amount of data (ie 199 mb) but still tell me that I have an open line contract (which I didn't request) and why if I was guilty of using the data, would they bring down a bill from almost R8500 to R1099<br> I don't believe I should pay this as this was not my mistake. furthermore, I am not the only person this has happened to this month. surely the mistake lies with Vodacom. please, watch out for Vodacom.