Out of bundle billing R3 000

<p>I phoned MTN to enquire about one of my numbers and was told that I owe them an extra R3 000. As I had exceed my data of 1gig.</p> <p>I told them that this line was over 2 years old and was now on a month to month basis. As I did not renew my contract. MTN automatically made it month to month and reduced the monthly charge.</p> <p>I had put on all my numbers a block that I cannot exceed the monthly contract amount with MTN</p> <p>I can also not understand why I was not contacted to tell me there was a problem?</p> <p>This line is used in the house with WIFI</p> <p>Is this ethical, is this good business practices? What can I do about it?</p> <p>How about all the times were I had not used my data and lost it ?</p>