MTN unresolved ********** account

For the past 3 months someone has **********ly been tapping into my MTN contract. Despite calls to MTN their reference numbers *** and ***, and a visit to a branch today, nothing has been done about this. Now to add insult to injury I received an SMS telling me I will be unable to make calls until I have paid the full ********** amount despite making an average payment today. I have been a client since 1997 and this is shocking service especially since not one person at MTN can tell me what they are doing about the problem. I am seriously upset at the service I have received about this and the total lack of interest shown by MTN to resolve the issue.