Getting ********** with data bundle

I have been a client of autopage for 15 years.My cell phone bill is on an average of r600 a month.On discovering a message sent to me to say that my unbilled calls is R2700. I was in absolute shock,as I hardly use the phone and it can be seen by my average spent.The first phone call I made TO Autopage I was told your balance is nil .I said to the consultant on Mon,then why was I sent a message to say my unbilled calls is R2700 he said he is not sure.I then phoned the following day again,and I was told oh its your network MTN as you have used 2.3 gigs of data.in a space of 5 days,which I normally use an average of 350 megs a month.I then get told its a charge from MTN that they charging you R2700 for 2.3 gigs of data,which is also strange as I used applications on wi fi.How can it possibly be that MTN can charge me R2700 FOR 2.3 gigs of data,when you can buy 10 gigs of data for R600 and I get told by Autopage you owe us r2700.It is disgraceful and a total ripoff that I must just pay a bill of this amount.I certainly hope that this issue gets investigated as a matter of urgency,as its impossible that from a monthly average of R600,i must now pay a outrageous amount.