Obc- Other Backward Caste certificate validity for the wards of defence personnels/Govt servants

Respected sir/ ma'am I humbly request you to kindly guide me on the below issue. My Father is a MWO in IAF (Personnel below Officer/Colonel rank), I am selected for FCI AG3 job. I am on OBC candidate. I submitted OBC-NCL certificate dated Feb 2018 and March 2020 to FCI but they are insisting for a certificate that is valid from 01/04/2018 to 31/3/2019 (FY 2018-19), as a result they have rendered both my above dated OBC- NCL certificates as invalid/outdated/expired. Secondly, I have been issued OBC- NCL certificate on the basis of my father's rank/position in Defence service not on the basis of his income (Father is MWO, which is below Colonel rank). But FCI is not willing to consider this criteria too, and is adamant that my certificates were not valid on 31/3/2019 . I humbly request you to kindly guide me on how to approach this issue with the Food Corporation Of India, what steps should I take and what reply should I sent because they are not understanding the above criteria.