African bank gave me poor and painful service and I'm now suffering because of their services

I had a loan in 2017 and 2018 I lost my job and I went to Soshanguve branch where I app**** for the loan to let them know that I can't afford to pay our agreed instalment and make repayment arrangements,but to my surprise every month they would debit the amount which I told them I can't afford anymore, I let it slide because I was going through a lot at that time,when I got a job again in 2019 I went back to them and they told me they can't find my account anymore.i decided to check my credit report and saw that the account has been listed,I still went back a couple of times to arrange repayment and still month end there was no debit on my account. this year I got a very well paying job and I was applying for car finance only to find out that my debt was written off as bad debt,my concern now is why was it written off as bad debt when I was making contact with the branch almost every second month making arrangements that never materialized because someone didn't do their job?when I had money I paid even more. Now when I went to African bank branch in Pretoria west to settle the account they told me I can't pay it anymore and African bank even owes me R100 and when I asked what it's for then they say it was my last payment. I'm very dissatisfied that an institution like this can actually neglect all the arrangements that I made with them and decided to blacklist me even when I had told them everytime I had lost my job and even went to an extent of making arrangements with them that were never honoured. Now I'm suffering because of that while I want to pay them off completely. So unfair.it breaks my heart that I never refused to pay them back but yet they can just decide without informing or contacting me that they are blacklisting me when I had made arrangements with them. It's so unfair. All I wanted was to settle my account with them .