One time option for conversion from new pension scheme to old pension govt of india

I am working in govt department where i joined on 19-May-2004. My selection process started in Dec 2002 with an advertisement in newspaper for 5 vacancies where i applied and called for interview in Aug-2003. There was no official declaration of result anywhere and i directly got an appointment letter dated Apr-2004. With recent order of govt of India stating that those cases of recruitment where appointment was delayed because of administrative reasons and their results were declared before 31-Dec-2003 and joined the service after 31-Dec-2003 will be given option to opt for old pension scheme. I want to opt for old pension scheme. When i approached my office i was told that since my appointment letter is dated latter then 31-dec-2003, i am not eligible. From the RTI source, i got to know that the candidate list ( including me) was sent to Minister office for approval in Sep-2003 and it came back in Nov-2003 with a general query. THen the file was kept by department till Feb-2004 and resent to minister's approval on Mar-2004 where it got approved and then appointment letter was issued. Since i was in selected list in file but because of delays of department it was not approved by minister before 31-Dec-2003. How can i justify this? They are saying that i have to approach CAT first then court. Is it correct way? any suggestion please?