2018 December faulty data overbill

I just got a debit order deduction for my account which was exceptionally high, upon getting hold of customer service they claim my data went out of bundle but cannot say with how much, what is wierd is that I still received an sms on the 29th saying my data was low but no sms saying it was finished, I still didn't use much data after this and my phone was rarely used with no video or data counters to prove other wise, yet somehow I used r1400 in out of bundle data according to vodacom in 2 days, my data counter Begs to differ using up and download totals. I feel ****** and most worryingly believe that all vodacom subscribers may have been taken for a ride on December 2018 billing as I don't think my case is an isolated incident at all