billing query

I could not believe it when my account was debited with R2219 for data usage in one month. For the past 4 years we hardly use 2 gigs of data per month and never pay more than the monthly payment of R149. After numerous calls and emails to mtn we still have not received an itemised bill explaining the data usage. I think this is very bad service as we not talking about a couple of rands but thousands. It has been more than 3 weeks without any feedback from mtn and I would like to know what is happening.