Why must I pay for ABSA's error?

Due to ABSA's incompetency, my last payment for my vehicle did not go off my account in March. ABSA changed the date for the final debit order. ABSA did not contact me at the time but did send me a 'notification of expiry of account' so my assumption was that all was done and dusted. I asked ABSA to send me the NATIS documents and the paid up letter but had no response form them. COVID and Lockdown then intervened but, now that we are on level 1, I went into the branch to ask for my documents only to be told that there was still a final payment outstanding. On enquiry I was told that this was a 'technical glitch' made by ABSA's system. I would like ABSA to let me know why they did not inform me in March or even in April that there was a problem, why I had to find this out myself sis months later, why I am now expected to pay for ABSA's error???