Unauthorized debits order

I want to know why you are allowed by law to debit my account before my debit date, this is not lawful, spoke to a agent asked to speak to a manager she just puts me back into the que, I WANT this DEALT with as its not treating customers fairly and I will report this matter. She advised a SMS was sent and I did not OPT out I don't see how that's legal the sms must sat OPT in because I made an arrangement to debit on my pay date not anytime before that money was my doctors consultation money who was today and now when o called the lady said no refund today bit you took my money today.