Noc

I am working as an officer since 5 yrs in a nationalised bank. Since, Apr 2016 , I was on Loss of pay, I write request letter to my branch manager every 89 days to sanction the leave period on loss of pay, but he replies that he has no power and advise to contact Zonal Head.I didnt getting salary for this leave period. Meanwhile, I applied for Sr.Manager post in Grameena BAnks and got a cal for interview with NOC. I didnt intimate my employer that i am going to write this exam. Can my employer deny NOC to attend interview .Shall i need to mention the future employer details while writing request for noc. I doubt our Zonal head may interfere and use her links to spoil my future.Kindly,advise.