Air Asia — air asia airline has cancelled flight. due to operational issue. but didn't pay the refund after 30 days

I have booked a flight from bengaluru to kolkata for 10th june, 2020.
Air asia send me a notice that, the flight has been cancelled due to operational issue. Still the airline did not pay any refund to me. Also the call center of the concerned airline did not responding. They received my call and the put my call into hold. Then disconnect the call. The details of the flight is given below.

Flight no:- i52990 bengaluru (Blr) to kolkata (Ccu)
Pnr no:- l1fcyp
Mail id:- [protected]@gmail.com
Contact no:- [protected]