Unauthorized debits

Fnb doesn't honor agreement with their clients, they do as they please with your money without communicating with the client, I have an agreement with fnb debit date is on the 25th whether it falls on weekends or on holidays, I don't get paid earlier than that period. Fnb goes on and debit 8 days before the agreed date! After I've specifically told them rather have your debit later than earlier, and then they want to charge me for the reversal of the debit which is their own fault! They are soo similar to loan sharks