Debit Order Mayhem

I have taken up a clientele legal plan from about September 2015 to date. I have sent them numerous email with regards debiting the monthly installment on my bank account at an inconvenient date which is the 23 of every month which I never agreed to. I get paid on the 27 and when I asked them they gave me some nonsense excuse about a company that collects debit orders on their behalf. I specifically told them I get paid on the 27 of every month and that is the date they eventually agreed to debit my account. Now I have noticed today 14.12.2015 that a debit order has gone off from my account and this debit was initially done on 11.12.2015 where does clientele get the nerve to debit my account without my consent? I have told them should this not be sorted I am going to be left with no choice but to cancel the legal plan this is the last straw.