I bought an open car parking space from a well-known builder in Greater Noida back in 2013, paying ₹1.5 lakh for it. It's mentioned in my allotment letter. Now, the builder wants an extra ₹50,000 to convert it into a covered parking space. Is it lega

I bought an open car parking space from a well-known builder in Greater Noida back in 2013, paying ₹1.5 lakh for it. It’s mentioned in my allotment letter. Now, the builder wants an extra ₹50,000 to convert it into a covered parking space. Is it legally possible for me to ask them for a refund or to convert the parking without extra charges?