Nedbank debiting my account for personal loan despite having paid in full.

On the 29 April 2021 I phoned Nedbank personal loan division to get a settlement letter for a personal loan I had will them. They email me the settlement letter and immediately that day I pay the full outstanding amount. Surprisingly they debited my account and even paid me a refund.

Today I have phoned them several times since I keep on debiting for April and May 2021 my account after I fully paid and instructed them to close it, they cancelled my call while I was on the line, the other one said I must hold will pick on another line but transferred me somewhere else.

As a paying client when I am not being respected and undermined it really makes me very cross, after having paid in the full, I do not understand why Nedbank keeps debiting me account.