UNISA debiting instead of crediting NSFAS payment received

My son received funding from NASFAS during the window period for 2021. Unisa instead of crediting the account has debited it and now it is reflected as being owed. I've paid for this years (2022) registration and am still being charged for what should have been a refund. I have emailed, no response. I've tried calling, no answer. We tried making an appointment, not receiving any slots. One just cannot reach Unisa in any way. I have also emailed NSFAS the query, also no response. In order to secure registration we had to take out loans otherwise risk loosing the entire year. Please assist.