You can change your Category during the correction window Karthik. The application fees is Rs. 1500 for General Category. EWS and NCL OBC have to  pay Rs.1400 and Rs. 800 for SC/ST/PWD/TransGender and the Payments can be made through Debit/Credit Cards or Net banking. Now if you change your Category from EWS to General Category, you will have to pay an additional amount of Rs. 100 during the correction window itself.