I don't think the pagers on the ship work the way you think. You don't dial a phone number to call the pager, they work like the pager they give you when you are waiting at a restaurant. The person wanting to page someone presses a button on a console.
Is there a reason you don't want to use the walkie talkies? A lot of them have a "pager" mode that should do what you want. If you set the radio's security code and set it to vibrate you will not disturb the other passengers. With the security code you will not hear the other people talking on that channel.