MTN DEBT WRITTEN OFF

good day i need assistance with advice or step further action on the following issue; i took a contract with mtn in 2023 mid year, then in November i was under debt review as i was struggling financially and couldn't afford any installments. in March 2024 i realized no account of mine was being paid - i decided to terminate debt review and called all my account holders and made arrangements. i called mtn in July and they advised that they closed my contract in June 2024 for nonpayment but it still needs to be paid as it was prepaid and during this time i only had the phones and no airtime or data was coming in so i don't understand why i was billed something i didn't receive. i was told i owed R40 800 which was the package of the contract and i told them i can only afford R500 per month as i just found a new job - all parties were in agreement - in august i started my payments. i then made means and paid all my outstanding bills so basically not counting my monthly expenses, MTN is my debt and biggest factor. i was contacted by Nudebt in April saying they were given my account by MTN and they want the full payment of 40k i emailed back saying i have an arrangement with them they cant take me to debt collectors then i sent all the POP since August 2024 till date. while applying for a car (which my family are willing to assist me pay for our family conditions) i am told i have negative expenses because it shows i pay a debt of 40k monthly so i don't qualify - when i check my credit reports from different institutions they say "mtn written off - bad debt" so it doesn't appear anywhere but as part of my expenses. i called mtn no one was ready to assist me the keep transferring me to different consultants. Nudebt i called and asked for a letter to say i made arrangements to pay they say they are waiting for mtn to transfer the money to them that i had already paid so i can continue paying through them so now i am really confused as they are ruining my name and no one has real answers for me. i need help to find out what's going on with this mtn account and if its written off why does it still appear and ruining my credit and why am i transferred to the debt collectors while i have an arrangement with them to pay R500 per month and they agreed?