Appalling service from Nedbank

I had a personal loan with Nedbank. On 4 Oct'19 I requested a settlement letter which they provided. I paid the full settlement amount within the prescribed period as stated on the letter. They then proceeded to deduct another amount from my account on 27 Nov'19, more than a month after the account was settled. I queried it and was informed that although the account was paid up, they failed to close the account. I requested that I be refunded which they promised to do. On 5 Dec'19 no refund was processed as promised and I reversed the debit order from my side. In Jan'20 a Nedbank consultant phoned me and told me that my account is in arrears. I once again explained the situation. She then said that I need to go to a Nedbank branch in order to have this sorted. I refused as I have done everything to their requirement. Today, I received another loan statement reflecting an outstanding amount. Why should I, as the customer, spend so much time (including having to complain in this site) to try and rectify an issue that was created by your incompetence, lack of accountability and oversight? Does Nedbank hold anyone in their employ accountable for their service failures or has this become an acceptable norm for the Nedbank brand as a Financial Service Provider?