Learned experts/members have valuable advice. Kindly follow it.
Ideally a/c should be settled and wages should be paid on last day in office or within 2 days. Usually companies set a time frame for FNF settlement however it should be within a reasonable time say 30 days.
Did you submit of resignation or resignation without notice, and did you submit company property and complete handing over the charge under acknowledgment?
You may submit a gentle letter to the good offices of your appointing authority, MD, Head-HR, Company Secretary and narrate all representations made by you so far mentioning name of company personnel and date of representations by phone, in writing, in person and request to supply you by redg/speed post acknowledgment/acceptance of your resignation, work experience/service certificate, FNF statement, settlement of dues and payment of dues by bank DD, form 16, relieving letter, PF number/accumulation reports/withdrawal-transfer forms, NDC/NOC etc, and mention that you are enclosing postage prepaid self addressed envelope for reply by redg/speed post only so as to reach you say within next 7 days. You may highlight that so far you have not received any response to your gentle representations as mentioned and you are seeking intervention and relief from good offices.
If the good offices do not provide relief you may lodge a complaint with o/o wages Inspector and/or issue a legal notice as deemed fit.
Relieving letter is issued post alls settlements at the end of employee and if nothing is due at your end employer should supply you the reliving letter.