UNIVEN CREDIT

2012 my university account was handed to Debt Tracker for collection of the amount I owed for dropout masters registration amount to R13 560. From 30 April 2012 they started to charge interest without coming into agreement for payment. April 2013 we reach agreement of R300 payment per month but my worry is that interest they sound to be very high. I requested statement because the credit was not going down then when I check the statement there are too many charges in one day and outstanding one was unrealised interest of R770 for July 2017 and when I made a request they said it's because I skip June 2017. Please help me to communicate with Debt tracker to make me understand their charges.