Jet Airways — refund of flight ticket

Address:

16 avenue gaur city 2 ,gr noida, Gautam Buddh Nagar, Uttar Pradesh, 201301

I have booked my flight ticket to Chennai from Delhi on 12th, but I got the SMS from jet airways- that because of operational activities flight has been cancelled by jet authority
So I want my refund
Flight details
UPENDRA singh-
Flight - 9w798
Pnr-DHHWER
TICKET NO[protected]
MITHILESH SINGH
FLIGHT- 9W798
PNR- DHOXJO
TICKET NO[protected]
DELHI TO CHENNAI- FLIGHT ON 12 APRIL 2019