MISSION IMPOSSIBLE TO CANCELL RECURRING DATA BUNDLE WITH VODACOM

I want to cancell a 30 day recurring data bundle, however it is impossible to do so. I tried options given without succes. I tried so called "Tobi", however he/she does not understand my request, he just wants me to buy more data, not cancelling any data. The only way now is to try and stop my debit order, but that on its own is also a mission.