Ripping people off- I will not have it!!

This company is clearly milking people and seeing other complaints, is clear indication that they are doing it to everyone. They sent me a letter of demand on the 10th June 2025 for an outstanding balance of R746.88. I made payments as follows: 10 June payment R627.96 27 June payment R118.92

When I sent her the final payment today they said I owe them an additional R256.73 which I had no knowledge about. This after her advising me on the phone that no additional fees will be added. They claim its a 10% redemption fee... how did they even get to that amount... 10% of what????