Unisa disqualifies student from studying after monies paid in full

my son is a student at Unisa, student no ***9, he paid in full for his studies for this semester(July - Dec 2019), Unisa excepts the money, however, sends an email rejecting him from studying and he has only 2 modules to complete his qualification, he sent an email asking for help, they refuse to assist or explain why the money was taken for the 2 modules, Unisa is not a good institution, there are many people working however, no one can assist a student regarding his studies, how many others are there like my son. And what happened to the money that was taken, why is Unisa making students lives difficult and not giving them resolutions, can someone in Unisa assist properly assist, or does people get paid to do nothing at all.