Air India — Cancelation of tickets and request for full refund

I had booked two tickets for international travel for my parents however my father died on 6th of May 2023 and hence my mother also can't fly.I had already asked for cancelation of both of the tickets however till now I didnt get any response from Air India. I talked to Air India customer care too and they told in this case we needed to furnish the death certificate and the ID etc of the person.I attached all docs, still no cancelation and no refund.What should I do?Date of travel is 17th May 2023.