Disappointed and disgusted

I have an FNB Account for more than 20 years. I paid up my personal loan account on 23 January 2019, a few days later I realised this loan account is still active and I contacted FNB that's when I was told because I did not request a settlement letter the amount paid was incorrect. There was an outstanding amount of R1587.12 which is for interest, insurance and service fees on a R0.00 balance account. I received a settlement letter that I must pay before the 19 February 2019 which payment of R1612.64 was done on the 18 February 2019. On the 26 February 2019 another debit order of R1943.05 was debited from my cheque account, now with tears in my eyes I need to know why this loan account was not closed when payment reflected. Was this debit for interest, insurance and service fee again, I have other debit orders going off my account and who will be responsible for the charges now. FNB needs to give my money back and be responsible for the bounced debit orders.