You did not mention about what you do currently. If you have passed 10th standard way back, then you will have to file an affidavit in the court mentioning your desired changes in the caste. If you file an application in the court, then you would require few supporting documents with you. I would suggest that you first approach the principal of your school. He or she will give you a certificate that you are a bonafide student of that school and you are stating a valid issue to the course. Hence, you deserve to get the mistakes corrected.
Along with that, you need to produce the OBC certificate that you have with you and a photo identity proof of yours containing your address proof. If you have a separate identification cards for photo and address, then produce the photocopies of both at the court. You will get your mistakes rectified in around a month or so.
Lastly, my suggestion is that in today's life caste is not a big issue. None of your career choices will be affected by your caste. So whether you are a general caste or reserved category doesn't matter, especially in the private sector. So why bother for such a minor issue? In case, you want the government privileges associated with the reserved category, you can go ahead with the above solution I mentioned. If not, you need not worry about this minor issue.
Live life Kingsize!