R200 failed debit order after successfully debiting my account

<p>My account was debited, in full, for March and the money was returned a few days later. Telkom says I "rejected" their debit order. </p> <p> </p> <p>On my April invoice, they charged me R200 for something the call centre agent admitted was a mistake on their side. Why should I pay this when the money was returned to me ?</p>