Utterly dissatisfied-Totally annoyed

I have an account that’s been handed over to MBD. I called them in January 2021 to make payment arrangements, I was told my balance is 55k and no interest and or fees will be charged on this account. I made payment arrangements to pay 2k on a monthly basis, I have been making payments and haven’t defaulted on any. We’re in September 2022 I get a statement that I still owe 42k. They can’t give me a details answer of why this debt isn’t decreasing as it should, they can’t provide me with a call recording of the calls I’ve been making and the initial call where I was informed that the only amount I’m liable to pay is the 55k. They tell me that my account is with DirectAxis and I need to call them. I’m at a point where I’m about to stop paying this account cause there’s no difference.