How do I report an MTN line used for fraud?

Depending on the peculiarity of the issue, if it is bank related, I will humbly advise you to report the issue to your financial institution as they have the jurisdiction to investigate the issue, if need be they will contact MTN on your behalf.

If the fraudulent transaction occured as a result of lost/stolen SIM, please report the issue to your bank first, then contact MTN to temporary block your SIM.

When the fraudulent issue is solely peculiar to your MTN SIM, please send MTN a mail at CustomerCareng@mtn.com with information on the issue experienced to facilitate their investigation.