MFC Robbing customers

The debt with MFC is a prescribed debt. They cannot locate the documents from the Bank for this account and still insist I pay the shortfall of this account. The vehicle was returned due to faulty systems in 2013. This year in January 2022 MFC a division of Nedbank posted an article that the vehicles sold in 2010 were faulty. That is when i made my purchase. I sent them the article published by the bank. MFC handed this account over to WJ Legal without my knowledge and further more without the documentation. I have been requesting it for 3 months now and they cannot locate it. they asked me to pay a 50% to settle the vehicle shortfall they sold the vehicle for. why should I? the fault was with faulty vehicles sold? why should be liable for the proof of documentation they cannot locate? Further to this there is proof of the faulty batch of vehicles sold which is when i made the purchase. Please investigate this case.