Consumer Redressal

I had booked a flight on Go Airways in the Name of Krishna Das on 22nd March, PNR NO W96DGJ, flight was from Kolkata to Mumbai and Flight no was G8 537/4/3 Departing at 16.25hrs. Due to lock down the flight was cancalled. the Airline informed us that the PNR No.is protected. The flight was statrted from 1st July from Kolkata to Mumbai. i have tried calling the GO AIR many a times and holded the line for more tha 2 hrs still there was no resonse. i have sent them email and they have acknowledged the mail via ref no.G8-01155051, I am sending them mail everyda, still there is no response, When i go to their web site and go to do the booking using diffrent dates it says[ Not authorized to change/cancel this flight. It is too close to the departure time.] using the PNR no. But if i go to do fresh booking, it is expecting the booking, My brother is stuck in Kolkata for more than 3 months, i am helpless as i am not getting any response. PLEASE HELP.