You can edit your SSC registration 2 times a year. Thus if you have done it then you can change the category next year or if you apply in any other next year then you can apply for it based on your changed preference. You can't change it now as your form have been submitted or you have agreed the changes for registration while applying for any exam this year.

Thus if you want to change the category then you can change it next year.

I hope this answer helps. All the very best for your future endeavors!