Non-existent account

MTN has sent me to debt collectors for a debt I know nothing of as I have no contract with them. The debt collector sent me to the branch when I explained that I do not have an existing account with MTN. The Branch could not help and I had to contact customer services who is now sending me back to the debt collector who could not help. All I want is my name cleared as I owed nothing to MTN!!!! Pleaaaaaseeee!!!!