As suggested on the above comment, if you have less than 1 years of experience and you really want to join the new deptt, then there is no need to obtain the NOC if they are not giving it easily. Just resign and join the new deptt. However if you have experience of more than 1-2 years, then you should talk with the higher administration about your condition. If the new deptt is willing to take you without NOC, you'll get a fresh start in that deptt. Your previous deductions and experience will not be counted in your new service