It is felt that:
-the position occupied by you in the company is such that you must handover the charge and material in store under proper acknowledgment and obtain NDC/NOC from your reporting/competent authority. This shall help you more than any one else.
-the time declared by company to take over is not reasonable. You may agree at 1 month.
-although company is resorting to verbal response you may minute all representations carefully with a copy to you, and build record.
The company might have announced this time to you looking into their need to find your replacement.
For taking charge and receiving company materials or property it is company's liability to designate an employee who shall perform this task and it can be reporting authority, HOD, replacement employee or any other personnel designated as competent by the company. For the point of view of separating employee it is no liability if company is not able to recruit replacement.
The very purpose of notice period is that company and separating employee can perform the exit formalities in scheduled time of notice period and accounts can be settled.
The employee should complete tasks on hand and train the replacement employee to perform tasks for the company efficiently.
It is goodwill gesture if the separating employee agrees to stay for a time desired by the company however the employee must obtain in writing from company that company shall treat the notice valid beyond the date of notice period and shall pay salary for the exceeded days.
Since you have drawn salary, even if offer letter/appointment letter was issued company can contend that appointment was accepted without order of appointment. However issuing no letter/appointment letter is not a good practice.
You may obtain copy of certified standing orders of the company which shall be available with HR/personnel dept. and may be kept at HR page of the intranet/web page for employees. Certified standing orders are to be circulated to the employees and kept at the gate. You are employee for the last 4 years and if all these years company has not supplied certified standing orders/employee rule Book Company is at fault. You are within your rights to demand it from good offices of the company i.e. MD/Head-HR etc.
Company may cite certified standing orders to impose notice period.
If certified standing orders are not applicable model standing orders shall apply. You can contend that no appointment letter was issued hence notice period is not applicable to you.
You may apply your rapport, goodwill, and persuasion, persistence, negotiation, reasoning skills and resolve the matter to your advantage while in employment and exit with a pleasant note.
If nothing works and employer becomes rigid, adamant you may approach a competent and experienced service lawyer with all record and give inputs and your lawyer may choose to issue legal notice or approach O/o labor commissioner.
