If you put wrong caste as BC D but really you from OC and correction time also gone, now only way is write request to exam board or authority, give proof of OC like community certificate, say sorry and tell it was mistake, ask them kindly to change it in their records, sometimes they allow change during counselling or document verification, but not always sure, so you try with all correct documents and letter.

1, Make one request letter telling about wrong caste filled

2, Attach OC community certificate and Aadhar or ID proof

3, Go to help centre or counselling office if possible

4, Try at document verification stage to explain mistake

5, If not accepted still, admission might continue under BC D only

https://engineering.careers360.com/articles/ts-eamcet-counselling