IIM Bangalore to cancel my candidature

Hi Guys,  

I belong to OBC category and I have applied to CAT 2016 as a 'NC-OBC' candidate. My father's income is less than 6 lakhs per annum and therefore my father had approached the authorities to get NC-OBC certificate.  But he was informed that the certificate can be issued only if both my father's and mother's income put together did not exceed 6 lakhs per annum and therefore they would not be able to issue NC-OBC certificate to me for this year.  

As I was not aware of this, I had inadvertently mentioned my category as "NC-OBC" while applying for CAT 2016. So in my CAT 2016 hall-ticket, the category is mentioned as "NC-OBC" and I'm requesting IIM-B to change the category from "NC-OBC" to "GENERAL" so that during the CAT selection process I will be considered as a General Category candidate. But they said it is not possible and my candidature will be cancelled if I don't produce a NC-OBC certificate. Can someone please advise as I feel helpless at this stage??

Also please note, I only produced a 'OBC' community certificate while submitting my application and not a 'NC-OBC' certificate .