billing and service very bad.

I receive daily updates as to my usage from vodacom. on Friday the 11 my account was R718.72. Saturday morning i received a text saying my account is R1400.96. When I phoned in, they said it was data usage. now Firstly I'm in the I.T. industry and have WiFi at home and the office and I understand how these things work, so I asked when data the was used they said 8:21 when I am at work (Have WiFi at work as well). Next I asked on what was this data used, they couldn't answer me... then the kicker.....they would contact me in 48 hours ... hmmmm looks like I need a calendar not a watch for this 1. Are they hoping I forget about the problem and pay blindly..... what can i do if they say i used data and cant prove to me what it was on? Referance no I got on Saturday was S3-9oc7p-pxsd. <br> I am a loyal vodacom supporter and have been for 18 years and now this. Leaves a bad taste in my mouth...