Definition of 'late payment' - advice needed

Hi guys

I had a direct debit to Creation Consumer Finance which I may have accidentally cancelled whilst cancelling a load of inactive direct debits earlier this month.

Direct debit is normally taken on 22nd of each month. I understand that direct debits take two or three working days to clear into the recipient's bank account.

They called me today and I paid the 'late' amount by card. Their website confirms that payments by card clear instantly. They've reinstated the direct debit from next month.

They would like to charge me a £30 late payment penalty. However, the way I see it, they would have received the funds today whether payment was made by direct debit or as I did paying with card.

My question is, was my payment late (is it the date of payment or date of receipt which determines whether a payment is late)? If it was not late, are they able to charge the penalty? They were unwilling to waive the penalty when I spoke to them by phone today.

I've asked them to send me a copy of the finance agreement.

Appreciate any advice.

Thanks

Stephan