Noc in psu banks

First i would like to ask who has a discretionary power to reject NOC to apply for other PSU under which reasons. Secondly if i applied for noc which was declined by authority without giving any reason and after passing applying date for other PSU then current PSU has given permission to apply, which is not possible as earlier declined and date has been passed, so how should i claim on my current PSU for my lost by loosing better opportunity. sir plz guide its urgent