Converting an unlimited contact to a limited one without the employee's knowledge

Hi,

I am resigning from my company after working for 3 years. I signed another contract after the first 2 years were completed.

I was under the impression that the entire time my contract was unlimited but now I am being told that it was changed to limited.

Not only was this done without my knowledge but I am now being told that legally I am not entitled to ANY gratuity after 3 years because I am resigning before my 2 years is finished. Is this legal?