Bill so far of R1611.55 for being \out of bundle""""

I have a 3 gig contract at R149 per month. On the morning of 20 August I logged on to the internet. I didn't download anything or watch anything and actually spent very little time on the net. When I closed the internet window I saw that my usage had jumped to 3.5 gigs in that short time. I immediately purchased a further gig online. Once again, it was only long after the fact that I received the sms that I was now out of bundle. After purchasing the extra gig, I looked at my balance on my Vodacom cellphone app, which showed the available balance as 1000.07 megs. I didn't used the internet after that and checked the next day to see that same balance reflected at 08:46 on the 21st of August. I phoned customer care and after a long wait got through to someone. Simple maths will tell you that 1000 megs deducted from 1000.07 leaves .07. So how was I out of bundle? No-one seems able to explain this anomaly. I received a call around 4pm from Vodacom and they said they would sent me the stats by email right away. I am still waiting for them. I want this fixed asap. Is this just another way of increasing revenue I wonder?