NTA does mention in its Information Brochure that Candidates cannot make changes to their application form once the correction window has been closed. NTA doesn't entertain any requests for changes to the application nor does it make any changes to the application on its own. And once the NEET results are declared and the merit list is prepared, the ranks are allotted based on the Category that you have chosen during the filling of application form. That cannot be changed. And so unfortunately, you cannot change your Category from General Category to EWS during Counselling.