Collecting on prescribed debts without an agreement

I received a message about a debit order that will go off from my account for a Telkom account. I have never received a call, message or an email from them before regarding the account and have not acknowledged the debt. The debt is prescribed but they are disregarding that and debiting our accounts ********ly. Although this time around, the debit order failed because there were no funds in the account, what they're doing is not legal. The account is supposed to be closed