Payment not missed but bank error occured

I was quite surprised to receive an email from HTN attorneys and I must pay Wonga account immediately. but the day 3 days before I received a mail from wonga that they had trouble debiting my account because of FNB and they said the problem is under control. Yesterday was a public holiday (reconciliation day) FNB debit ordered my account I thought the problem was solved on the bankside but to my amazement, I still received a threatening email from HTN attorneys. The reason was that the previous day was a public holiday and wonga did not inform them to stop. I am very confused they knew FNBwas at fault for the debit order miss hap yet I am being threatened will legal action. This is highly unprofessional behavior and the FCA should probably look into the company because looking at wonga track record I am not the only person suffering under their authoritarian regime