Frustrated whether i am liable to pay the collection commission interest?

My husband is being handed over to Saya Recoveries he owed Capfin. He made an arrangements to pay the amount he could at least afford, since 2016 till current. When he requested the statement in November 2020, capital 9099.42 already paid 6050, according to Saya he was only paying the cost and fees. Now the outstanding balance is 7 038.53. I have asked whether he is liable to pay commission interest till when? Is fair ? If you add 7038.53 + 6050 (paid) =13088.58. Is he liable to pay commission interests and how long should he pay interests? At the end of the day debt it is not reducing instead it increases. He was told to pay R1500 going forward. He can not afford that amount. The frustrations is more and more. Am i missing something here. ***