Unreasonable settlement rejections after settling R37,500

I have been trying in good faith to settle my handed over accounts with DMC. Two weeks ago, I settled an account for R37,500, which I paid in full. I appreciated that discount and paid immediately. I then tried to settle my remaining, very old handed over accounts and offered R17,000 as a settlement. This offer was rejected . These accounts are very old and I am trying to clear my name. I am willing to pay, but I am looking for a realistic settlement discount, just like the one I received two weeks ago. Rejecting R17,000 outright feels unreasonable and being told to go and raise more money and pay next year was very bad customer service. I would like a manager to review my requests and provide a fair settlement amount so I can finalize and close these accounts. Reference available on request.