Phonebills ranging from R6000 to R15000 on REDVIP

I am on the Red VIP contract with Vodacom which is unlimited, except for your data of which you have 3GB apparently. I always have my phone on Wifi when I am home (I work from home). Plus I bought an additional 10GB and again 2GB of data last month off my device for the device which is appearing on my bill. So how do I ring up R 10 000 worth of data if I have 3GB to start with, bought an additional 12GB AND I AM ON WIFI!!??<br> When I went in-store (where they cant tell you anything because Vodacom is franchised (so you must phone the helpline) They said the following: Since I am on am open plan, the data I bought can not be used and the data would have been billed as per normal. Secondly, when on wifi it doesn't mean that your data isn't being used. So why do you have a wifi option on your phone to save on data if it is using data anyway!!! It is absolutely unacceptable to think I pay R2200 for the top of the range contract just to get phone bills of R10 000+ next my phone will be cut off because I DO NOT HAVE R10000 LYING AROUND which will affect my credit score and payment history. Absolutely RIDICULOUS!!!!