Vvm debt collectors claim i owe MTN

I received an sms from vvm debt collectors stating that i owe MTN an amount of R25000+. I then went to MTN and they lodged the case with the ***** department. I went to the police station to make an affidavit that says i do not have any kind of account with MTN. Vvm kept on contacting me. I told them ive already sorted this out with MTN. I send them a copy of the report from MTN more than twice however they still harrasing me, calling sending messages. This really frustrates me. Please help. Thank you