[Resolved]  Noc — Builder asking money for NOC

Hello,
I had booked a flat and have got the possession of the flat.
I had borrowed some money from friends and relatives to buy the flat. As I have to pay them back I want to go for mortgage loan against the flat. Banks have asked me for NOC from the builder. When I approached the builder, he asked me for 11000rs. Of which he wont give the receipt also.
I want to know:
Is it legal for him to ask money for NOC?
If yes than how is the amount decided?
Why he is not giving me the receipt?
Where and whom should I approached?
Kindly help with the suggestions and reply at [protected]@gmail.com