TERMINATION NOTICE

I am currently working for a MNC and my probation has been confirmed by my current employer which my original contract of employment stated a 30days notice is required if I would like to resign. However, the HR Dept recently issue out a memo to all Executive with a personal letter to me that the terms of condition of employment has been changed and notice period for termination is now 60 days or 2 months in lieu which I declined personally and refused to sign. This is because I am not happy as there were no increments upon confirmation and I planned to look for a new job soonest possible.

Is my lawful termination notice period 1 month or 2 months as I have NOT sign the letter of changes in terms and conditions?

Your feedback is very much appreciated.