How to make a legal complain against society for not transferring the flat?

It is useless to get entangled in legal process. If it is possible try to solve the problem amicably with the Society. You have not mentioned about what objection the society has raised. In any case, if you wish to court, you have to approach a Civil Court. Think thousand times before you take this course as it may take years together to get a verdict. It is time consuming and expensive too. The only beneficiary would be advocate.