In case you are determined then submit gentle communications: first verbal, then written (narrate verbal communications in it) under proper acknowledgment.
Remain amiable.
Obtain salary slips.
If these are backdated; point out verbally, then written.
Build irrefutable written record.
Avoid discussing every day, and writing every day.
Once you have separated with acknowledgment and acceptance of notice of resignation/final resignation, service certificate, reliving letter (with good comments), Correct FnF statement, Form16 as per Correct FnF statement, PF a/c slips of all months, ESIC card, NOC/NDC, acknowledgment of handover of charge, clear BGV etc etc ………………….you can rake up the issue.
If there are employee’s unions, Works Committee, Grievance Redressal Cell………………..it can look into the matter.