Unjustified interest and collection fees

I feel exploited by this company called brooks and luyt attorneys. My Truworths account was handed over to them since 2022 , I made payment arrangements and started paying my account. I noticed that the amount was not decreasing even after paying consistently with no missed payment. I requested a statement thats where I realised I was being exploited. There is interest and collection fees that are being added on daily basis. The total amount on the 25th was R1270.96 today when I request another statement the amount has increased to 1326.16 but I have already paid my monthly installment. Is this even acceptable for the amount to increased while the arranged amount is being paid on time and in full. How are these people helping us settle our account when they are robbing us like thi. Totally unacceptable. I have paid other collection agencies with no trouble, amounts were settled without any unexplained additional fees.