MakeMyTrip India — Fake ticket issued and now denying for refund

Address:	MUMBAI
Website:	make my trip application

I had made a booking from mumbai to nagpur.
When i reached the airport i was informed that the ticket you have been showing is not valid as the pnr number printed on the ticket is not valid.
The pnr number is generally of 6 digits but the pnr on our ticket was of 5 digits which was issued by make my trip.
After talking with make my trip they promised us the refund within 45 days.
And now 3 months later they are asking us to bring a conformation letter from the airline or else they wont entertain us.