Open parking

Hello Team, I seek your opinion regarding how to approach for open parking dispute with the builder. I have booked a flat way back in MAy 2011 at Atlanta Enclave, Shilphate, Thane. At that point of time the sales person told that sale of parking has not started and hence in the registered agreement the builder has been silent on the open parking but he has clearly mentioned about no parking in the stilt area allocated against my flat. However when he offered possession to me this July 2017, the sales guy has asked for Rs 2.5 lac per open parking that too in cash. few resident owners have already paid and got the allocation letter from the builder. What should be way forward advised to me? Regards, Ritesh