Mbd attorneys ripping me off!

In May 2017 I received a call from mbd attorneys that they are taking over my standard bank cheque account from previous debt collectors that my account was handed over to, when they took over it was almost 2 years I have been that account, and when that account was handed over to the previous debt collectors the amount was around R6000, early this year I requested a statement from mbd, I was shocked to find out that i only paid R1600, and the capital is R5871,balance R4271, I asked them that how is that possible because I have been paying for over 2 years, the statement only shows what I only paid them but not previous debt collectors, they told me that standard bank is the one responsible, I requested the detailed statement from the day I started paying this account till today I'm still waiting, in February 2018 I requested a statement again, then capital was R6104 balance R4304, I queried about it I was told about standard bank, last week 25 July 2018 , I requested a statement again and the capital is R7302 balance R4502, I was told about standard bank again, my query is why does capital go up? I am paying this account for more than 4 years but capital and balance goes up every day, I thought capital is what has been handed over to the attorneys, why does it have to go up every day?