Notice period Waiver

Can the employer reduce the notice period date? Hi , Appreciate if you can help me on the below query. I have recently resigned from my employer. I submitted my resignation 90 days prior to my last working day and mentioned my last working day in my resignation. However, as per the employment contract, I have to serve them a notice period of 60 days during the probation. My employer has now changed my last working day (for eg: If my last working date was 27th of Jul they changed it to 30th of June mentioning that you only have to serve a 60-day notice. Could you please advise if they are allowed to change my last working date? As per my understanding, it was a minimum of 90-day notice. However, I could have provided the resignation before that mentioning my last date. If they want to change the last working they have to terminate me on a minimum notice of 90 days. Also, please let me know if I will be eligible for annual leave encashment and repatriation allowance.