Paternity leave eligibility in psb

Dear Sir/Madam, I am Ananth , scale 2 officer at Gujrat in india post payment bank which follows iba rules. My son was born on 24.01.2018 at my native state TamilNadu . At that time i was working at Postal department which is direct central government. I was working there till 09.03.18 and had not availed any paternity leave while working there. I joined india post payment bank on 26.03.18 and applied for paternity leave as per their leave rules which states that the leave should be availed only upto 6 months from the date of child delivery. At first Postal bank asked me a letter from my previous employer that i had not availed paternity leave while working there. I had submitted it now. But now they are refusing my leave over phone stating that i will be eligible for paternity leave only i am a employer at the time of delivery of my child. But this point is not given either in iba rules or ippb leave rules or central govt leave rules. Hence please guide me whether the view of HR department of my bank is correct. Else how can i proceed further to avail my paternity leave of 15 days if i am eligible as per rules. My six month period expires on 23.07.2018. Thank you Sir/ Madam, Regards, I.Ananth, Deputy Manager, Ph: 9865419495