Parking issue even after getting an allotment letter

I was the first buyer in the year 2007 and resident in a new constructed building and accordingly after purchasing the flat received and allotment letter from the builder / promoter or dedicated car Parking for my vehicle in the building. The builder / promoter has given me a letter of allotment along with demarcation of space drawn on the paper. Since I was the first purchaser of a flat in the building I was given the option first come first basis and allows to selected the parking space I wanted which I did which was convenient had an independent entrance as well. I gave the above document to the society as well for their records which has been accepted. Everyone accept One of the new buyer of a resale flat who bought a flat in 2018 is calling the letter illegal and forcefully parks his vehicle in the space allotted to me and even after repeating requesting is not willing to remove his car from there. I have written to the society bears as well requested the society as well but this particular flat owner is a bully who has contacts in the BMC so he throws his weight around and does not listen to anyone in the building either What can I do what are me legal right please advice