Although you have mentioned your designation as Asst. Manager still you may show all employment related docs examined in detail and designation and nature of duties examined by an able Labor Law Consultant/Service matters lawyer and your counsel can opine if you shall be covered by the def. of 'Employee' as in Shops & estbs Act, 'Workman' as in ID Act and standing orders (model/Certified) shall be applicable to establishment/your designation.
If yes the notice period/notice pay shall be covered by these enactments and these shall prevail upon appointment letter and may not be necessarily 90days.
The T&C in contract of employment should be equitable or thses can easily be termed arbitrary.
Does the condition of acceptance of notice pay in lieu of notice period is also as per discretion of employee if employer has initiated separation by termination?
Has the Operations Manager/HR Manager declined to accept notice pay in lieu of notice period in writing? If yes have they stated the reason also?
Do you have copy of notice of resignation? Did you tender notice period of 90 days and applied for waiver?
Did you apply for waiver of notice period or offered notice pay in lieu of notice period?
Both are different!
Did you mention that NO Tasks are pending at your end and to whom you should handover the charge, and ciet all appreciations,rewards,awards, and that no stinkers/show cause notice has been served on you etc?
Downlaod all rules, policies,mentioned in appointment letter, awards, appreciations, rewards, appraisals etc ASAP.
It shall be better if all representations are now structured and drafted by your able counsel and are submitted by letter under proper acknowledgment or atleast from personal email id and are addressed to/or with a copy to appointing authority,MD etc.
Does your next employer agree to buy out the notice period/rpvide extention/absorb you without relieving letter/ even if adverse comments are posted in BGV?