NDS Credit Management busy reaping me off and their service is terrible

<p>I lost my job in 2013 and couldn't afford to pay my STD bank credit card and my account was handed over to NDS Credit management. On the 24-11-2015 I did request a statement from NDS Credit management and according to it my outstanding balance was R16205.66 and Total Balance due was R16669.64 and I was so shocked and still am after receiving a statement which I requested on the 05-05-2016, which states that my oustanding balance is R13606.24 and my Total Balance due is R14070.22,my monthly payments for end of November and December 2015 was R500.00 and from January till April 2016 I have increased my monthly payments to a R1000.00 all in total I have contributed a total amount of R5000.00, on the 06-05-2016 I called NDS Credit management to query that as those figures didn't make sense, and I spoke to A lady by the name of Patience who WAS NOT PATIENCE ENOUGH AND RUDE AND END UP DROPING MY CALL and when i called again she did transfer as she did fail to assist me and end up transfering me to Nomalanga who couldn't provide me with the clear explanation and said she will refer the matter to her supervisor who called me later that day who failed as well to explained himself but promise to investigate what could be the cause for the figures not go down and promise will come back to me within a week and I am still waiting. all I need is a clear explanation of how did they get to this latest Outstanding Balance from R16205.66 to R13606.24 after they debited a total amount of R5000.00, how much interest rate and collection fees and commision do they charge me, Because thats a discrepancy of R2400.00 and that is a lot of money for someone who is recovering from unemployment and has other debts to pay as well. </p>