NSFAS employees taking our payments for themselves.

I have been paying my loan through stop order from my bank since 2014 January, earlier this month NSFAS sent me statement then I went through the statement I found that two installments are not appearing in the statement and the balance is still high, then I called NSFAS to enquire about the installments of January and February 2018 they took me up and down saying they will rectify the mistake even today they haven't done anything, they expect me to pay the whole outstanding balance.