If they do not release your dues, then think in terms of legal action.First try to meet higher officials and keep your discussions in writing and acknowledged.These acknowledgements can be useful if you have to approach courts(Last resort).
What was your role in the Company ? Why NOC is required from Dealers? Does your role involve any cash handling between Company and Dealers. Not sure. If any uncleared funds to be settled with the company based on your role and responsibility then employer may hold the FF. However talk to your HR or Employer and sort it out amicably.