Here's the Simple Version of the prop for the PDC I've been working on. Note any similarity with a certain Robo phone is purely coincidental! For the version which can be used to store preset messages, simply cut away Tab X, and the darker line below it. Also remove the entire 'lockscreen' so you can see the message below, if you want to get really slick, you can glue a piece of plastic inside.
EDIT: Oh, also for best results, print on 60# or heavier card stock