Still waiting for a refund

I request a refund from the Nimble Group on a Capitec account that I had overpaid. I was told that the process will take 20 working days. I submitted this request on the 7th of July 2015 and to date i have not received my refund. I have on numerous occassions contacted the call centre and everytime I am told to wait more days for my refund. Its been a month now and i still have not received my refund.