Query regarding Data depletion with once off bundle

I logged a call at Customer care on 23 August (Ref 1- ********** ********** ). To date I have had no feedback or response. I received an SMS on the 25th August asking if my query was resolved, and to reply NO if it wasn't. Which I did. Still no response. I'm tired of Vodacom *****ING (yes this is what you are doing) data. I bought a 500mb once off data bundle on 22 August, on 23 August I got an sms to say I have less than 250mb left. This is impossible, I'm connected to wi-fi all day, did not download apps or videos, did no updates. The next day I got another sms saying my data was below 180mb. And every day it's just gone down to nothing. 500mb normally lasts me a full two weeks if not more. It is impossible that in three days I used 400mb. Someone needs to get back to me urgently. I've been waiting for a full week for you to "investigate" I want PROOF as to exactly what that data was used on, and where, and for how long, because I know that it is impossible. This happens every single time I buy a once off data bundle.