They take your money any day they want even if it is not the agreed debot ordr date

I signed and agreed for my debot order to go off the LAST day of the month. I accepted teh Debicheck on my bank for THE LAST DAY of the month. But Connect Finance chose to deduct it any time that suits them , and take my last money . If the last day is on a Sunday or Public Holiday, they don't care, they will take it any day that suits them. Even if my salary is not paid in, and they take my money that is meant for other things. Without my authorization! Is this not breach of the agrement? How can you take money from my bank without my knowledge and authorization?