Covered parking vs open parking

Hi,

I own a flat in Hadapsar, pune. But at the time of buying I opted for uncovered parking. Now as per builder there's a covered parking available for sale. When I asked what changes will be done in agreement, he said that since he can't sell parkings now(as per new rule), he'll increase the agreement cost and issue me a Letter of Allotment. My question is doing this will I face any problem when society will get created, and will this make me legal owner of that parking?

Thanks,
Sadashiv