Bad bad service

I took a loan with Nedbank a few years back, due to the Covid pandemic I was struggling to pay it because of a salary cut at work. As things are starting to get back to normal i eventually managed to settle the account. On the 16th of February to be exact i called their call center and requested a settlement letter, i was aware that i was 2 months in arrears so i was under the impression the letter would be inclusive of everything. They sent the letter to me and i paid the full amount assuming i would then be done with the account. To my expectation there was no further debits or communication from them. Suddenly almost 2 months later thet send me an sms that they are unable to debit my account. I was surprised by this so i logged a call to their customer service line and i was attended by a very rude agent who kept telling that it was my fault that the account fell in arrears and that i should have known that the settlement letter did include the arrears. My question to him was how come did the settlement letter NOT include everything, even the arrears and why thet did not inform me of such for almost 2 months. He could not answer, he just said i needed to pay what ever amount is still outstanding.