Vodacom App faulty and data to be cancelled

last month on the 11 July i tried to activate 3 gig data for one of my vodacom contracts. halfway through the process it showed their was an error and i left it deciding i cannot afford it. I then noticed a couple days in August that there was data on my number and when i received my bill I saw the 3gig data that was not suppose to go through did. We left it as we needed the data and already started using it. Today 21 August I tried deactivating it from the app and it did not want to. I then proceeded to call vodacom and was advised that the pro rata amount charged on my July bill will be disputed as their was no data allocated and i'm being charged. I'm happy to pay for August data received as we used it and no problem. But now i want to cancel as I cannot afford it on my next statement and im being told it cannot be cancelled as im in arrears. It does not make sense if im arrears and im telling you i cannot afford that extra 3 gig data of R300 certainly it must be cancelled. I CANNOT AFFORD IT AND ITS DUE TO YOUR APP NOT WORKING RIGHT THAT IT WAS ALLOCATED IN THE FIRST PLACE. I NEVER EVEN RECEIVED ANY SMS OR COMMUNICATION THAT THIS WENT THROUGH. I'm very upset and I'm going through difficult financial time. I'm also a loyal client of over 8 years if not longer. Their must be some way of cancelling this as i will take this matter further as i said i cannot afford it.