Pay Fixation during Probation

Sir, I have served in the armed forces as a short service commissioned officer for 10 years and got retired post completion of 10 yrs of service. After 04 months of my retirement I joined another central govt job as a Grp A officer. As per the existing rule of pay Fixation for retired Short service officer, the pay in the civil post is to be fixed after granting advance increment to the completed years of service in the armed forces i.e. 10 increments in my case. Therefore, i represented my application regarding granting me 10 advance increment in the pay level I have joined. But the organisation, sent me the reply stating that the re-fixation of pay will be considered and taken up only after successful completion of probation period. I want to know that is it legally correct that the pay Fixation will be done only after successful completion of probation period. Since I am eligible for the advance increment from the day I have joined the civil post therefore the fixation of pay is to be done at the earliest and it should not be denied quoting the probation period. Sir, I want to know the legal aspects and the right guidance from you.