Extremely saddened

I have a personal loan with Absa which has been in arrears...I spoke to someone from Absa some months ago to make a payment arrangement of 500 as that was all I could afford at the time which was to be debited from my account...now I received a journal debit of 2000 which I had not authorised and when I called in to query it, I was told they cannot reverse it and it was debited because "my account is in arrears and the lawyers were not able to get hold of me telephonically." I have an e-mail that works just fine, and I did not dispute that my account is in arrears...I do not even know which lawyers I have been handed over to as I was never informed and never authorised such a hefty amount to be debited. Being a single parent and having to calculate and account for every cent I spend, I am now left with literally nothing to get through this month, school fees, rent not yet paid. How can a bank I have been banking with ever since I was old enough to be transacting be so heartless and not care at all about my query. Both ladies I spoke with did not assist and are unable to reverse this transaction. Can they please debit the 500 and return the 1500 so I can at least buy groceries for myself and my child. PLEASE 🙏