Rejected debicheck mandate

I rejected a debicheck mandate on the basis that I have no business and have not app**** for anything with that provider (CellC) however FNB still allowed the debit order to go through. It means we are not safe from *****sters if our own banks will not be willing to protect us as their clients. I haven't been able to dispute or stop that debit order because it exceeds a certain threshold and I tried doing it via money assist but the option to attach the affidavit does not work. I layed a formal complaint regarding this on the 26th of April via the FNB website but I never received any feedback.