Mahindra And Mahindra Car - Car Booking Amount Issues

I booked XUV*X* online by paying the booking amount Rs ***** to Mahindra in early January.
The car was delivered on **th Feb and when I paid the remaining amount, I was asked to repay the booking amount as that money didn't reflect in Dealership's account from Mahindra. Although, it was dealership's and Mahindra's internal matter, I was still forced to pay this money and told that they won't be able to issue gate pass unless this due is cleared.
I was promised that either Mahindra or Dealership will credit the amount back in my account within * days in a signed letter from the dealership. Now it's been around * months and still I haven't received my money back. This is not only causing financial instability but also mental stress on me.
Dealership's address:
Mahindra United Automobiles - SUV Showroom
Metro Pillar No. ***, **/*, NH-**, near NHPC Chowk, Block A, DLF Industrial Area, Sector **, Faridabad, Haryana ******