Learned Mr. Raj, Mr, kameswarao have given valuable advice. Kindly follow it.
Employer is duty bound to supply you the FNF statement, work experience/service certificate, relieving letter. You are within your rights to lodge a complaint with o/o Labor inspector mentioning date, time, phone numbers ( yours and of HR manager), in person representation etc. You may demand that this HR manager should be called in person along with policies of the company stated by him/her.
Employee should record (audio/visual) statements/representations which shall be useful later in an appropriate forum. While you may submit a letter to company kindly ensure that it is addressed to your appointing authority and details of the statement of this HR manager is mentioned by you, and policies of the company stated by HR manager are demanded by you.
It is for sure that the statement of this HR manager is verbal and has not been issued in writing and the concerned policies of the company stated by HR manager are not supplied to you.
Relieving letter is issued post all settlements and you have settled even the notice pay. You are a good employee. This company and this HR manager should express their gratitude rather and should happily issue not only work experience/service certificate, relieving letter, but a good conduct certificate.
work experience/service certificate, have their own role, use, and are certainly required for your future ventures e.g. immigration, work visa etc. Would you again start the process when it is demanded by some other employer or for your future ventures, and suffer? Why you should give up your rights?
You should bring the matter to its logical conclusion.
This HR manager is probably not aware of the implications of treatment meted out by him to you and that he/she shall have to face the brunt of it. HR manager is duty bound to point out to his/her employer while deciding the policy or even while applying a policy which has been finalized by his/her predecessors, that their policy is wrong/unfair/illegal.
Anyone involved in formulating or implementing an unfair/illegal policy is to be treated as offender.
In your case both the policies of the company and actions of the HR manager are unfair and liable to be awarded reprimand and penalty.
As rightly advised by learned experts/members if you lodge a complaint and add force, it shall be rewarding for you and many others.
It is their funeral and let them handle it.