Paid up loan

I had a personal loan with FNB, The loan was settled on 18 October 2018 by paying R74 655.70. The statement confirmed that as well as records on the app. Around 28 November 2018 on the app it showed that i owe FNB R840 which was labelled Interest. I inquired why there were interest when the loan was paid up, i was told it wan an error and it will be rectified and was also informed that the amount i paid was extra. On 14 Dec 2018 my account was debited R1171 for a personal loan, i called and was told it was in error and it was refunded. Again on 24 Dec R1171 was debited, i called and was told that its an error and it will be refunded. R314 was paid into my account, i called again and was told that the full amount will be refunded, however none of that has happened. I'm tired of calling FNB everyday for the same thing.