Want to file a Case against MAke My Trip

Hello, My Parents had booked a domestic flight (Raipur to Delhi and back) air ticket with MakeMyTrip.com on dated 27th April. They had received confirmation mail with air ticket enclosed with PNR number and booking ID. Ticket cost was 14,500. On the day of journey, when they reached Raipur airport to take the Indigo 6E-204 flight for Delhi, they were told by the Indigo staff at the airport that the PNR number does not exist and there is no ticket on your name. On calling the customer service of Make My Trip, they have verified the booking and found that the booking is canceled by mistake from their part. To get the compensation, she asked us to book a fresh ticket at the airport itself and save the E-ticket and invoice document for reimburse the amount and send the same through the customer support link. My parents saved both the E-ticket, Boarding pass and invoice with this message. The fare they have paid is 31,920.00 INR To get this money reimbursed, I had to follow-up with Make My Trip more than 50 times and each time to re-iterate the same story and ask for the reimbursement. Finally, My parents got the difference money today after reaching all way till the head of customer care. With this experience, I should say that it is a lesson learnt for the next time that never to book any airticket from Make my trip rather booking with the airline directly. Now, I would like to file a case against MAKE MY TRIP on their carelessness and giving all this mental pain. My parents are old-age and we had a visit planned to number of places in Delhi. But die to this incident all day I was busy calling them. I want the trip should be free of cost and they should also reimburse the 14,500. Do let me how can I get the justice. Regards, Amit Sharma