Unfairly treated

Hello peter I had a loan with DMC Debt management that worth R17 000 which was R10000 and R7000. During the cause of the year I lost my job and couldn't afford to pay my loan as pensioner. I went to the salary management services( SMS) for them to help me pay my loan with a low priumum and without interest and my first payment was made on the 24 July until July 2019 and all in the money I paid when ask for they say is R24000. 00 and also told me that am still owing R22 487. 90 so I didn't understand because I already paid more than I owed. So I need help so that they can clear my account cause according to the money I paid I don't owe them any more I think they taking advantage of me cause I am a pensioner. Kindly help me on this matter. Regards Annah Ngobeni.