Account handed over even though it was fully paid

We received a sms stating that the account is in arrears and has been handed over. How can that be possible when the account was closed and it was paid via debit order. Now explain to me how that is possible that this account could be closed when there was money outstanding. When you call the debt collection agency, all they tell you is the amount that is outstanding and they can't give you the statement showing that the amount is \owing"if it ever was. When you send an email to Telkom"