When you access programming of the DNA-510, make sure you program a touch tone operation command to play the desired message (and pre-alert tone if there is one).  Program “11#31” to set up the touch tone “1” to play message one.  Programming “12#32” would set up the touch tone “2” to play message 2, etc.  This is described in the product manual at the top of page 7 and Chart 3.