Early Debit on my account

Miway debited my account 1 day before the agreed debit order date.

Their policy document states the debit will go off the working day before or after if the agreed debit order date is a Sunday.

According to the consultant, Saturday is a working day for debit orders, but who or what needs to service the debit order before my pay day.

My debit order date was on Sunday in September, but the debit order went through on Monday.