Air India Express — Air Ticket - Refund of cancelled Flight

I had booked 4 tickets on PNR# VGUVNB on Feb 10th 2020 directly with Air India Express on their webpage.
i have been requesting for refund since 27th May as the flight was cancelled by Air India Express.

I contacted customer care and they mentioned it cannot be refunded.
Later when the CS phone number was reached after several international calls and also holding for a long time, they told me to contact nodal email id but their would be delay in refund.
I send several email to [protected]@airindiaexpress.in but with no reply or answer.

I request complete refund .