Refund for paid flight

A flight was booked and paid for but when passenger got to airport, they didn't let her on the flight and she had to pay cash for another ticket. I was told to check the bank statement and if the payment has gone off then i need to send it to the refunds department. All requested details were sent an was told it will take 7 to 14 working days for refund. Its has now been 2 months and still no refund. I am told on 3 follow ups that manager has not approved it and will be done in 2 days. Still no payment has been received. Disgusting service with mango airlines !!!!