Data Useage

At the end of Feb 2018 R5,876.32 was deducted from my bank account for payment for my wife's cellphone account. On querying this I was told that R5000 was for out of bundle data useage. As we have Wi-Fi at home and mobile data on phone switched off could not believe this but could not speak to anyone who could give me answers. Today they sent me a CDR report for totally the wrong period. About a year ago I got a high data useage bill R1200 which was due to my wife not connecting to Wi-Fi and using mobile data which I then went to MTN and requested that they ensure that when free minutes and data are exhausted then the account is capped, I phoned MTN to check that this had been done and they said yes the account credit limit was set to zero. Now they are saying this is not the case it is only for their internal use.