regarding parking rule in rerra

Sir i bought a falt in noida extension in unjbera project with free open car parking and its written in the booking form also now the builder is forcing us by writing a letter in which he is telljng us to take compasry covered parking and against this he is charging 3 lakh rs... I want to know is this justified and wht rerra says abkht parking ir it compulsory to take covered parking... In my bba also its mentioned open car oarking but bba signed in 2013.. Pls help me out