Cannot get feedback after cancelling contract

I enrolled my son for Grade 10 but he could not write exams in April due to illness. I was forced to pay for the exams. I then obtained a a sick note advising that he was unable to write the exams and that due to his illness, he could not complete the year, I am still being charged and they wont refund me the R 3900 exam fess, i have over paid R 5200 for a service i have utilized. Dealing with Nolene Adams and Reolan Naidoo, is proving fruitless as they dont get back to anybody. Waiting 3 weeks for a simple reply. I dont like to slander anybody in public, but what else must a person do to get any customer service?