Struggling to get a refund since November 2015

In November 2015 me and my husband had our first experience in flying with Mango. Very excitedly we decided to reserve specific seats. For this service we had to pay R55 per seat and it was return flights which mean the total amount we paid was R220. When we arrived at the airport they told us a smaller airplane was being used and that our reserved seats are not available. They advised us to phone the refund department and they will pay back the money for the reserved seats. They provided us with a number to phone and for days we tried to get hold of anyone. Arriving at the airport again for the return flight once again a smaller airplane was used and our reserved seats was not available. Another number was given to us to phone for the refund. As mentioned above this was in November last year. We are tired of trying to get hold of anyone. The numbers provided just keep on ringing with no answer and according to the Mango personal that is the only numbers we can phone. Booking reference MYGNYF. Numbers provided *** / ***.