SC certificate

I have joined Directorate of Brick Production through PSC Clerkship exam 2004 as unreserved candidate. Later on & before creation of vacancy for promotion, I have submitted my SC Certificate. Can I be treated as SC and considered for promotion as reserved candidate as per 50-point roster ? My office didn’t bother to do any PVR of my certificate and put up in the Service Book. But, now they are not considering me for promotion under reserved vacancy. They are saying that my candidature is supposed to be treated as unreserved as per PSC merit list and based on unreserved vacancy.
Now, candidates below my rank are due for promotion based on their reserved category rank.
Kindly help.