NSFAS unresponsive

So i studies on NSFAS. On 25 July 2019 I received a statement with a small amount that I still owed them. I immediately payed that amount. On 27 July 2019 I received a statement with a much bigger amount that I still owed them. How is that possible? I contacted them on 31 July 2019, 12 August 2019, 15 August 2019 and 22 August 2019. Today is 2 September 2019 and I am still without an answer. They are quick to send statements but when there are queries about the statements everyone is quiet and not responding. This is very frustrating.