Debited my account on a date prior to agreement

During the month of December Norman Bissett & Associates took the liberty of debiting my account 8 days before the end of the month. I returned their debit order unpaid, as this was not within the agreement. Since then I have been called on a daily basis by the consultants , and none of them keep record of the conversations, not one note at all. I have requested a letter that they will honor their agreement in future for debit orders, but as the consultants are not making note, nothing has come of that. I am awaiting a senior of the company to phone me to resolve the issue.