Dmc unfair treatment and miss informing customers

I called in to settle my payment which was R10000 so an agent who assisted offered me a settlement of R7000 which was around 30% off if I paid once off the agent offers to call me back she never did instead the sent an email with a link of different payment methods and discount went through with the agreed payment of R7000 pay off or once off used their banking details even got confirmation they received the payment but now they sensing me email that I still owe the R3000 and something while we agreed on the amount of R7000 I tried calling the even sent screen shorts of the email they sent to me and asked them to listen to the CALL by they never called back sent emails they are not responding and it's messed up my credit score can't even get a job because of them willing even to report them to the ombusman office my number is *** have never received such a bad treatment for trying to do the right thing and they saying they can't give settlement letter