NSFAS failing to reduce balance on account

I have been in communication with NSFAS since November 2015 up until now and no one is able to assist me. I received a grant from FASSET in September 2015 which was for the payment of my NSFAS student loan and have been communicating with NSFAS to found out if they have reduced my loan balance with the grant FASSET paid on my behalf. I have emailed and called NSFAS numerous times and sent them the proof of the grant to no avail. The loan balance still is accruing interest on a monthly balance although they have failed to reduce this balance.