No communication

I have changed my subjects for this semester and paid the first installment but haven't received my study material or any response from Unisa. I've mailed countless times asking for assistance and called administration but either the line is busy or the person doesn't answer or the phone keeps on ringing. I honeslty don't know anymore as I have to pay the second installment but feel that I should at least get my study material before then and the status on MYUnisa is still awaiting payment.