A. Generally, car parking slot has to be mentioned in the Sale Deed with the flat number, UDS and super builtup area but no car parking slot number could see in the same agreement. Some builder will issue separate letter by allotting number towards the car parking slot. Moreover, the car parking area would come under the common area which cannot be charged. And sometimes car parking slot determined by the builder depends upon super builtup area.
B. In your case, you can demand to exchange car parking area instead of present car parking slot and the builder reserved more than two or three extra car parking for visitors or their use. First, you have to get still floor plan to know all the car parking areas and identify the remaining car parking area which is not allotted to anyone and tender demand for that area.
C. We cannot come to conclusion as to it is violation of agreement unless verified the clause of the agreement in respect of car parking area. For Your Information, the builder not having right to claim charges towards the car parking slot because of it is treated as common area as confirmed by the Supreme Court.