REFUND NOT PAID

I have made changes to my flight, due to my wife being ill and not being able to board a plane, I contacted mango and made changes, they assured they will issue an credit note, I went to the airport and they said I need to fone customer care, I foned and everytime the consultant said it will be issued the ffg day, until I insisted too speak to a supervisor, in which case i was shoved from department to department holding on the line for 45 minutes until they finally put the call down on me, I have sent numerous emails where I recieve no responce from mango, ive been travelling with mango airlines for the past 6 years and I am totally shocked with the way they treat customers, I am waiting for them to issue a credit note or refund from the 31-01-16 up til today, I have already booked new tickets, with the loss of my refund... and. I still await responce to my emails and phone calls...