Disappearing Data

So my data is disappearing and marks 2weeks and Vodacom is still sending me their report that shows how my data is spent. What is still a bone of contention is that when speaking a Vodacom rep they just assume that it is internet usage however not presenting other alternatives there could be that is causing my data to disappear. Was told that someone will respond and this was week and to date still waiting for that Vodacom rep and now received my Sept bill and sitting with an exorbitant amount to pay on data I didn't use.