Truworths not so transparent

My truworths account was handed over to MDB attorneys last year. The opening balance upon making arrangements with MBD in 2015 Feb was 13700, I have made 3 installments of 1000. Today when I went in store to pay my account has a balance of R11 100. When I call MDB I was told that my actual balance is 12300. This alarmed me as I was told that the Truworths balance is not a true reflection of what I really owe. This is a lack of transparency from MDB and Truworths because both balances need to correspond so the customer knows how much is really owed. So this year I have paid R3000 on R13 700, yet I currently owe R12 450. The MDB consultant nor the Truworths consultant could account for where the R2000 is when reviewing the account payment. It is not transparent why Truworths and MDB have differing balances and how much is really owed, nor the interest rates or the nature of interest. In this regard Truworths has not been helpful in explaining the conditions of being handed over and in the process has led me to falsely believe that I am paying off my debt when the debt seems to compound with every payment. I don't have access to the total amount owing or how interest is being charged.