Someone has opened an account IN my name!!!

<p>I received a call from some legal firm informing me that I have been handed over by MTN for non-payment! I NOW have a mark against my credit score! I DO NOT have an account with MTN!</p> <p> </p> <p>I want to know how this account was opened? And by whom! And why are the proper checks not being done! And I have not been contacted at all by MTN for "non-payment" and just automatically handed over! I want this to be sorted out immediately and my credit record cleared!!!!</p>