Unauthorized Debit Order.

My Account was debited R1000 this morning by Network collections, I don't know what it was for because I don't have an account with them. I called them 5 Times already and the same person is picking up the call she is telling me that their system is offline I should call back after half an hour. I sent them an email no feedback. I need to understand why I was debited and what for as I want my money back.