I would ask HR to clarify. It's your right.

but instead of accusing them of being unfair, I would let HR walk me through the guideline (or logic) first. There might be something you were not aware of. If HR tells you that everyone of the save level has the same package, it's your turn to mention that you noticed that it might not be the case. Let HR explain. Regardless, stay calm and professional. You don't want to burn the bridge. You never know when you will cross each other again.
Good luck.