FNB and debt Review update nightmare!!!

I entered into debt review in 2017 and have been making prompt monthly payments to Debt Busters for the past 2 years. My outstanding debt for my overdraft account with FNB was R21 315.08 thus far I have paid a total amount of R15 693.82 to FNB through debt busters but I am sitting with a balance of R22 234.56???? I have logged this issue with Debt Busters who advised me that FNB never adjusted the renegotiated interest rate on the account TWO YEARS LATER???!!! They followed up and FNBs response was that they were behind with updating their system...!!! My intention is to settle all my debt by 2020 and at the rate that FNB is dragging their feet to fix this problem and back date my correct interest amount seems that my dream of being debt free is not likely to happen. I need someone from FNB to contact me and explain why this is taking 2 years to finalise when my payments are received on time every month. I need to speak to someone who can assist as this is a highly concerning matter that FNB seems to not take any notice off. I am very, very angry and upset at the lack of professionalism displayed by a company of this size