Address your letter to :
your appointing authority, and MD/CEO, principle offiecer of your company,CS,HR personnel with whom you had telephonic represntations, HR Head,your reporting authority,your deptt. Head and mention that you had the matter of your resigining from the company with your superiors and as per amicale decisions you left after completing all the tasks assigned to you and your superiors issued you NDC relieving letter and assured that F&F shall be supplied within....days.
You have been waiting for the same and have reminded toMr............on Dated...........at his phone number...............and by email on ............at his email id.............
After serving the organisatin to the best of your ability and to the best of satisfaction of superiors you feel that there should have been no need for reminders and F&F conatining all dues to be paid to you nincluding.............(all mentined by you) should have been paid to yu by now, and that you request the good office of ...............(your appointing authority, and MD/CEO, principle offiecer of your company,CS,HR personnel with whom you had telephonic represntations, HR Head,your reporting authority,your deptt. Head)it to be paid within......days .Ask for an acknowledgment.
If it does not elicit response,you can issue notice.
You may post the details as adviced by learned members/experts of the forum for their further advice.