ABSA - bringing unflexibility to life

I have been an ABSA client for the last 15 years. My home loans and car loans have been with them all this time. I have never skipped a payment. In June they didnt debit, i only noticed at the end of August that they are not debiting. I immedediately contacted them. They are now threatening me with interest and putting my name on a blacklist as a bad payor because of their error. I have offered R500 per month extra to square and they dont want to budge. Unreasonable and unflexible bank.