MTN is trying to **** me!!!!

I'm a Vodacom customer and haven't used MTN for the past 10 to 11 years. I recently found out that I 'owe' MTN an amount of R12 000 and I've never had any contract with MTN. I tried calling the service call center and non of them have been able to assist me as they have been transferring from one department to another. What they would do, the call center agent would just be rude to you and just transfer your call to another department without even notifying you. This is so frustrating as my credit score is being affected and I'm afraid for MTN because clearly our information is easily leaked out to *****sters.