Unsatisfactory Feedback

I contacted the vodacom call centre re my airtime balance and an amount of R85's worth of airtime having disappeared within minutes. A service request was logged S3-8203O-O4Kia. i was on the internet for 5-10 minutes at most and vodacoms explanation is that we pay R2 per MB for out of bundle rates. That sounds like a generic response. it does tell me exactly how i lost R85 airtime in a matter of minutes !!! They need to tell exactly how that was deducted cause the above still doesn't make sense. I have used airtime for the internet in the past and have NEVER lost so much in such a short space of time. A breakdown would be great cause i trully dont believe that this is possible