parking rules in India & illegality?

one private sector place where many people come for the computer-based exam and who's ever is coming is in 2 or 4 Wheeler they are charging 2 twice as mall basement parking lots, here just an open parking space but no display of the amount of parking the person, however, is giving parking slip but once I caught him as he was asking different amounts from a different person... is this place illegally charging the parking fee?