NBE has laid some rules regarding Category. Once the correction window has been closed,  NBE does not guarantee that any request for change in information will be entertained. It will not make changes on its own either. Once you fill the application form and the correction window is closed, what you enter there, stays there. And the merit list is prepared according to the Category you have chosen at the time of filling the application form. And lets say if you cannot submit a proof of OBC-NCL you will not be considered General Category. Your admission will stand cancelled.