carparking can be converted as building?

Dear Sir/Mam, I have purchased a independent first floor ( I am the second owner). Description of the property Total area 4800 sq feet Block A 2400 sq feet groud and first floor. Block B 2400 sq feet ground and first floor Open space between the property 7x60 sq feet. As per the actual approved plan 3 car parking (front side of the building) for each black. Block A was constructed as per the aprovel plan. But, block B insted of single flat in ground floor, made into two flats. They converted the car parking as another flat. So, there is no provision for car parking. My purchased house was first floor B block and it is being rented. My previous owner didn't informed this issue. He showed the open area as car parking . The owner of ground floor now enjoying the two flats. One flat he occupied and another he gave for rent. He also utilizing the open area for his car parking. He is not allowing my tenent to park his car. Even Block A person also creating some problem. When compare to all I am only having the highest UDS (1380 Sq feet). My question is Can modify the approved plan from Single flat to double? Car parking can be converted as building? Who is having right to use common space as car parking? Can I move this issue legally? I have spent more than one crore. Kindly sugest me to solve my issue