Why do you think a decimal 15 value will make the Speakjet stop repeating itself?
There is nothing in the datasheet to suggest that. It say that value will make the voice
sound relaxed.

You say this makes the Speakjet repeat the string over and over
Code:
Main:

serout 7, T9600, ("at your command\15")

goto Main
but if you leave out the goto cammand it will never say anything?

Might I suggest that the Microchip pic has powered up and sent the serial command
before the Speakjet has become ready to receive it?

Try this:

Code:
Main:

PAUSE 5000

serout 7, T9600, ("at your command\15")

End
and if that works, see how low you can adjust the pause value.
Art.