Notice period extension

Terms of employment cannot be changed at the whims of the employer. Proper procedure is to be followed along with the acceptance of employee is required to change such terms of employment. In your case, there is neither acceptance nor proper procedure was followed. You can easily resign with one month's notice period in terms of your appointment letter. 

Hi Ritesh, Thanks for the reply. Below is the email i received by HR back in 2018. I replied and told as i am not accepting it. 

My query is if it is an  amendment ( clause 5.1 which i don't see in appointment letter might be they kept the company policy somewhere) will this mandatory be even if i not agree to it ? don't i have the right to agree or disagree ?  The below email came with HR signature, not with letter pad or any CEO signature. 

"In furtherance to the Appointment Letter issued, we would like to inform you that there is an amendment with reference to clause 5.1 that your notice period has been extended for 2 months instead 1 month as per the notification received from the client.
If this notice period is not served for any reasons, you will be bound to make the loss suffered by the company and any other charges/liabilities Company/Client incurs.