employer is trying to do separation pay instead of retirement pay

Separation from employment must be done in good faith for it to be valid. So, if you were chosen specifically to be separated just to avoid retiring you, then you do have a case for illegal termination. Also, find out from the DOLE Field Office nearest you if your company had already filed the required Employment Establishment Report which reports the planned separation. If they haven't filed it yet, then this is already an irregularity. You do need to explain more about this situation, i.e., how many affected, what was the criteria for choosing you or all of you, are there similarly situated employees that were not given notices, what was the reason for the termination, is the reason supported by documents or events?