unfair treatment

bought a ticket to Durban for 21 December 2018. and i could not travel and called in to cancel the ticket. was promised that i was going to get the refund in 15 days till now i have not received the money. been calling them and not getting straight answers when i ask to speak to speak to the supervisor was told by the call centre agent that they don't have a supervisor. been calling them for the past 10 days and i'm not getting help. called again today and still getting the same story that manager is not available. i really need help as i need my money back plus interest for inconveniencing me so much that i have to call everyday and on their side there is no communication . Thanks,