********** Debit Orders

Each month a debit order is actioned on my account from a company / person I never had any interaction with. Every month I call in to FNB and ask that a block be instituted on this debit order for maximum period, but it keeps on going off. How can FNB process debit orders that are ********????? Why do you not stop it as I requested for the past three months!!! I DO NOT KNOW WHO THIS OR HOW TO STOP THIS ********** DEBIT ORDER!!!