Endless Payments to MFC

I took a vehicle account in 2013 with MFC, a year later my financial situation drastically changed, I got into debt review ,MFC was one of the accounts that was under debt review, which means at that time there were new conditions payment arrangements and interest, after some time, MFC withdrew from Debt review and became independent, i was paying MFC the full amount independently,( in my understanding, the fact that MFC withdrew from Debt review it means once again Terms and conditions must change either to the original terms and conditions or to new T&C's).however Mfc reviewed the account and credit some of the interests back or cancel it,, initially when i purchased the vehicle i had Balloon Payment of R27 000.when i got into Debt review it moved to R57 000, when MFC withdrew from Debt review they never took it back to R27 000, i sent several emails requesting for explanations no one bothered to answer me, in June 2020 i finished Paying the vehicle in full remainder of the Balloon payment, MFC stopped contacting me until January 2021, They call me and told me they made an arrangement for me to pay the Balloon for new 36 Months, which we didn't discuss or even me agreeing to , I was on phone one time with one of MFC representatives, I said i will only Pay R27000 Balloon payment and she said no i Have to pay R57000 over 36 months, I sent mails over and over to MFC requesting for this issue to be resolved, the only response i get is LETTERS of Demand, Accumulating interest and collection Notices, MFC I am not Happy with your Service and i will not allow you guys to drag me back to bad name on credit bureaux.