Data dispute & process of notification of data usa

I have been trying for more than a month to resolve my data dispute with Vodacom. I do not want to talk to yet another consultant or their manager as it only resulted in Vodacom telling me that their data information is 100% accurate which is definately not the case for me and judging from the numerous, harsh comments on their facebook page it seems like a common problem. I have been a vodacom customer for more than 20 years and have always paid my bills on time but now would like to cancel my contract ASAP. I renewed my data and cellphone contract in Jan 15. Vodacom has always notified my when I am about to run out of data. This did not happen in Jan 15 when my data account (which never exceeded R200/month) was more than R5000! When I called them I was told that the information is correct and when I asked why they didnt sent me a notification as usual, I was told that it is a courtesy to notify me not an obligation! This after they set the expectation for years! To top it all off, they started sending me notifications again the very next month where I depleted 800mb during a weekend away from home and my WIFI was switched off. Now you tell me how accurate is their information?