Hey aman!  Thanks for asking us. 

You may not change the category from general to obc for the sake of admission and it may also be a crime. 

But if there was a mistake and if you have certain proofs that you are obc then you can contact with the management and do it. 

Thank you.

Hello Aman thanks for reaching out to us.

you cannot change your category officilay but if you have accidentally chosen wrong category and have valid proof for your category  can contact the committee and apply for change in category