Additional cost when settling the loan

I decided t settle my personal loan early and went on the Capitec App to settle what was owing. To my surprise there was an amount of R80.41 which was listed as arrear interest. I sent them an e-mail querying this on the 9th of April 2019 and i have yet to receive a response. I then had money deposited to my account and as soon as it came in it was debited by R80.41. I am frustrated by the bank as they still have not explained what this cost is made up of. I can't understand why it is arrears interest as my loan was paid up to date and in full. Please urgently respond.