Refund request

I app**** to study for the second semester in 2019 but later cancelled my studies after I had paid for the registration fee. I went to enquire about the refund process and was told if I submit the necessary documents I should get my refund within 15 business days. It's been more than 15 business days but no communication from Unisa with regards to my refund. I've called their land-line number and I was on hold for over 30min then the call was dropped. What does a person have to do in order to get their money back.