Dear applicant most often when you apply for any particular Examination, during your application whichever category you submit it remains your category till counselling and admission. After admission you can ask your college authority to make a change in your category and get the desired facilities. But yes whenever you apply for any exam, next time, you can add up your EWS certificate and upgrade your category. For better efforts send a  mail to enquiry mail id of the examination authority for updated category.

Good luck!!