Mr. Chandrasekhar has given valuable advice. Kindly follow it.
The appointment letter should promote equality. The terms and conditions as expressed in your appointment letter are heavily weighed towards employer as employer can terminate the contract even before expiry of notice period and can decline to accept notice pay in lieu of shortfall in notice period.
Then as mentioned in this thread, your employer is ordering you to remain on board even after the expiry of notice period, by extending the notice period by another one month.
Employee should avoid abrupt termination until or unless there is some exigency and should explain the exigency in notice of resignation. The purpose of notice period is to grant time to employee to firm up his/her next venture and to employer to find replacement, complete the exit process and relieve the employee. There are companies which charge the employee for having caused them loss due to abrupt termination.
You may tender reasonable notice and express your effective date of resignation/last day in office in the notice and if you feel you can mention the fitting and suitable reason of separation. You may offer to adjust notice pay in FNF statement. If your next employer is buying out the notice period, you may avoid payment of notice pay to first employer by cash, cheque as you may suffer double taxation. Let your first employer reduce your amount of FNF settlement by adjusting notice pay.
You have posted that “I am currently working in HCL and have decided to leave the company now as my mangers have started surrounding me and giving me hard time.”
Employee should endeavor to remain amiable and maintain decorum. However, if the line management steps on the toes of employee should gather evidence and prove the bad conduct e.g. audio/visual/witnesses, which if required can be produced at appropriate time in appropriate forum.
Employee has the discretion of reporting the incidences to good office of appointing authority, MD, Company Secretary, with a copy to Head-HR. If the evidence is on the employee’s side, company shall be on weak foot. Companies are known to coerce and transfer the onus on employee and create a situation where employee ends up either suffering loss or falling in litigation. Be smart.