Data billing inconsistency

I was billed for R1800 by Vodacom in one day for data. This is very inconsistent with my normal usage and so I paid and lodged an inquiry into the transaction. I have been a loyal customer for many years and pay my bills on time without fail. The way the query has been handled has been quite disappointing as this was in June and I'm still waiting. I don't see how that much data could have been used in one day. They kept making mistakes with the forms which we then rectified but still no progress. I paid the amount as I did not want to be in areears but I would really like for this query to be attended to quickly and with a sense of urgency. We also normally turn offl cellular data when we are home as we have wi fi in the house so it is highly unlikely that that much data would have been used.