Shocking ********* behavior and practice

I was handed over by Discovery for a small part of the annual savings that went over after I terminated my membership. I made an arrangement of R 100 that I am paying over every month. In April 2023, I requested an outstanding balance - R 666.00. August 2023 I requested a settlement amount, thinking that I only owed a last few rand in view of the April balance. Surprisingly, my settlement amount is R 315.91?? Upon my query regarding the amount i was told they will send me a statement. Refuse to answer any questions. Just confirm there are additional fees every month I pay, but refuse to answer any questions. It appears an individual will never be able to settle an account with them??????