Itemised billing for data usage

On 31st Dec I had data but on January 1st I had no modem connection. After several inquiries I was informed that I had exceeded my data bundle to the amount of R1212.25. I have had the same contract for several years and have never yet gone over my limit and in December my computer usage had not changed in any way. I requested itemised billing for that period so I could identify if perhaps my computer was downloading from the internet without my knowledge. I also found it strange that it all happened right at the beginning of the month and coincided with the time that Vodacom had a huge billing problem. Apparently I also had a R1000 credit limit, (1st time I have heard of that as I would have set it at R50 which is apparently the minimum limit that can be app****), however the bill I received was for R1212.25. I have twice been promised the itemised billing within 24hours, ( a report was sent from Sandton Data store which I visited and once following a call to the accounts department), and 3 weeks later I am still waiting for a response. My reference number is S3-GJE2K-K4L6H