No feedback for a refund

I mistakenly paid cell c R499 in April 2015. I did not realize that my last installment was the previous month, March 2015. I then lodged a query with them and I was told that the refund would be resolved in 7 to 21 working days. After numerous calls, I finally got through to someone called Octavia Mnyoni, and she requested me to send her the proof of payment, this was on the 14th of May. She was then supposed to call me back. It is now the 25th of May, and no, i haven't received my money back and or a phone call.