Air Costa — air ticket cancelled not refunded for jai-blr flight

I had booked a air costa flight through their official website in march 05 from jaipur to bengaluru.
The flight was cancelled due to reasons unknown and we received a mail that the amount shall be refunded within 15 working days.

However not received the refund amount of rs.4056. I have sent so many reminder mails and they every time revert saying 15 days. Its more than 5 months since the cancellation has happened and i have still not received the refund amount. Now their system is not accepting the mails also.

Hope this forum would do something in getting the refund amount.