I think it is best to discuss it with the Labor dept or an attorney. However, I do not think the employer can unilaterally change the terms of the contract especially the notice period. From what I know the minimum notice period for the first 5 years of employment is 1 month and then 2 months for 5+ years. Since you signed a contract which stipulates a 2 month notice period you must adhere to it and this cannot be changed without both parties agreeing to it.

If your contract states a minimum duration of employment i.e. a term that you must work before your contract is renewed then you must complete that. If you do not have a clause that allows you to resign before the expiration of the contract then you might be in a bind.

You must get a copy of your labor contract and can approach the labor dept to help you get one. I know they are strict about these things and a complaint, or several complaints should get their attention. Again, I am not an attorney but can just share my opinion based on work place experience issues and word of mouth. Good luck.