Absa ruining my life

I had a cheque account with Absa, I then stopped using it as i was nologer working an i sent an email to absa for my account to be closed. When i stopped using the account it was on a positive balance and after a month or two it was closed.. out of the blue today i received a call from a collections company telling me that my Absa account has been handed over to them, I don't understand why my i was handed over because according to my knowledge i dont owe Absa anything, my name is just being ruined for nothing.. To make things worse, when i enquire about this nobody gives me a straight answer. where can i report them?