Extremely Bad Response

I'd like to express my frustration and disappointment on MTN credit management team. I was lately contacted by a company named VVM introduced themselves as a debts collector of MTN whom they brought something to my attention that almost drove me crazy. They've told me of the account I do not know of and demanded that it should be paid. I went on and on about this and requested more details in connection with this account they're referring to and was asked to send through my particulars to proof my innocent but had no joy of it after all. I then requested TransUnion to investigate this matter and they came back and say MTN has not responded to any requests made to them and advised that I should rather approach any of their branch to have this matter attended to urgently. That has been done and every store I go to they don't seems to know who I should talk to or any valid number for a credit centre. I was once given a number of *** for ***** Dept but there's never anyone at the end of this lines. Now, I've been a victim of impersonation and logged several calls via a ***** report link but that did not seem to HELP either.