Home loan - Incorrect debit order loaded

My further bond was registered late in December, 6 days before my debit order went off on the 26th December, the amount deducted was still the old instalment. I though this was due the bond being registered so close to the debit order run. Then on the 26th January the new instalment was deducted as I expected.

Now I see Fnb has since marked my home loan account as "not in good standing" as they only deducted the new instalment amount in January and not in December.

I would like to query as per FNB's contract agreement terms. As I signed up for debit order, should the onus not be on FNB to deduct the correct amount as I signed payment method in the home loan agreement? There was also no communication from FNB side to raise this in a timely manner in the month of January.