Pay fixation and counting of past service rendered with indian army

Sir I have served with indian army as short service commission officer from Feb 2009 to Dec 2015. In Dec 2015 I joined indian revenue service through the authority letter issued by DoPT on the basis of exam conducted by UPSC. I appeared for the exam after taking permission from the Ministry of Defence through proper channel. On receiving recommendation letter from UPSC I informed Ministry of Defence about my selection. Later, on receiving the joining letter for the same I requested for release from service to join new job in civil, again through proper channel. After receipt of approval from competent authority I got released from the service and joined the training academy. My resignation is technical as per the process, however ministry of defence didn't mention in the approval letter. On completion of probation/training I applied for pay protection and counting of past service rendered with indian army. However, my request has been rejected by the department of revenue. Need guidance from your learned team regarding legality and further course of action need to be followed. Regards Maj Heera