Flight missed due to the staff’s mistake. And to make the refund of the amount.

Hello Sir/Madam,
This is Aayushi Maheshwari. I was travelling from Chennai to Indore by Indigo flight on 2nd June 2016. Mumbai was halt in between. the flight for Chennai to Mumbai was 6E 495 and for Mumbai to Indore was 6E 496. My PNR for the first flight was J6BJQF and for second flight was J6BJQF. Due to some reasons I missed my second flight i.e. from Mumbai to Indore and the reasons were, me and my friend were sitting almost in the front of the boarding gate no. 13 as specified in the boarding pass but the screen on gate no. 13 never showed us Indore..it was displayed Hyderabad so we were waiting for it to display Indore. Later when it was high time i.e. 20 minutes before the departure we went there to ask about the boarding of the flight then your staff said that the boarding has been closed and now nothing can be done and that’s how we missed our flight. I know our mistake was i should have seen the flight no. and i also agree that, that terminal was silent one..but we never knew that the same flight was for Indore also. We talked to Indigo’s staff members for giving reaccomodation in the next flight for Indore but they asked us to take a fresh ticket again from Mumbai to Indore inspite of having a plenty of seats in the next flight. That was not our mistake completely, its the duty of your staff members as well to make us known to the another flight..there was no other option for us rather than taking the fresh ticket. So, I request you to make the refund of Rs. 4583 for us. The PNR for my fresh ticket flight was R7YJUF. But inspite of all of this, they gave us our baggage in mumbai only by making it remove from the flight, if they can do this why did they didn’t make us sit in the same flight.
I hope for a fast reply and please I request you to consider my problem.
Thank you!