My department is making the delay in issuing the noc

Hello sir/madam, i am a central government employee working as ldc in indian bureau of mines and i had applied for assistant post (level-4) in isro and i should submit the noc to isro within seven days after my application, as per instructions after applying to isro i had applied for noc to my department, it's been 20 days after applying for noc but till date there is no intimation from my dept and the stipulated date to submit noc is over , if i dont send the noc to isro does't consider my application and i will not be allowed to appear for the examination itself .why should i give up on such a better jobs than that of my present job just because of the delay of my department? what i have to do for this type of dalays and injustice i dont have any remarks on me and no action pending to issue a noc not only for the above said job, my dapartment is dalaying in issuing the noc for applying for other jobs also , if i keep silent on this issue i will not grow in my life and miss a lot of opportunities due to age constraint and limited eligible notifications when ever i contact out hq people they are saying again and again that the application has to go to the ministry what i have to do for this injustice and how will i get justice thank you