Mango Airlines
Flight booking refund

I had booked a flight to visit my parents in April 2013, however my father passed away suddenly in March and I had to book an emergency flight for the funeral. I cancelled the Mango reservation KTJKJT and the call centre agents directed me to fax over a copy of the death certificate, which I did.
A few days later I followed up with Lucinda/Lusanda to determine what I should do next and was told that she was on leave and would get back to me; I've had no follow up from any Mango representative to date.

I would like to use the credit from the cancelled ticket towards a flight to visit my mother at the end of this year. I've spent the past hour bouncing through the call centre and eventually I was just disconnected.

Is there anyone who can assist me with this simple booking request?
I need a flight from JNB to CPT departing 29 Dec and returning 6 Jan 2014.
The R1803.00 balance of credit from cancelled flight KTJKJT should be put toward payment of the new flight.