MTN undue debt

MTN's account system is one month behind which did not present a problem until I received an sms from MBD Debt Collectors claiming my account is in arrears, which it is not. The female agent explained that it is a system error which was escalated but could not give me re-assurance that this would not happen again. In fact, the reference number allocated to the alleged number does not even belong to my account. She rudely disconnected the call when I asked a reference for my call, to ensure that it does not happen again. MTN, what is going on?