No refund

My partner and I flew back from Cape Town on 15/5/15 and had excess baggage of 24 KG, after paying we realised we had been charged for 44KG. On querying this, were told by Mango Customer Services in CT Airport the refund would be done within 3-4 working days. I phoned Refunds on 26/5 and was told they knew nothing about it and could I send an email plus documentation, which I did within an hour and I even included the baggage tape which clearly showed the total weight. I received a read message the same day but no response and when I phoned today they couldn't find my email. After hanging on for 16 mins I was told Chantel was awaiting a report from the airport. Unacceptable customer service - they wouldn't wait for their money.