Refusing to give me paid up letter

I had a loan with Lendplus, and I was retrenched, which made it impossible for me to pay. They handed over my account to Landau. I got a job and called them to make arrangements; that's when I learned I was handed over. I negotiated with Landau; they provided me with a settlement letter. I paid off the account a long time ago, but they have not updated it. I have been calling and sending emails requesting a paid-up letter, but they are simply ignoring me. Please give me my paid-up letter.