Bank account not debited but adding arrears

I received a call two months back from a guy who said my credit card account has been handed to them for collection. I made an arrangement to pay R500,00 monthly via debit order and it has never happened<br> <br> I am getting worried now because the account is obviously adding more interest/arrears while I have always had money on my bank account for them to debit. I told the guy that I don't want to promise him that I will make cash deposit but would like them to debit from my bank account. I gave him my banking details but till today they still haven't debited my account<br> <br> Please find out why this debit order hasn't been successful and advise