Originally Posted by floydr

The way to do this is to go into shortcodes in manager and append all of the shortcodes telephone numbers with s1234567890 ( lower case s plus 10 digits that you want to substitute) that start with your dialout prefix in brackets, [9] in my case , to what they were: for example In my #[9]0n shortcode the telephone number '0N' becomes '0Ns1234567890'.. You have to do it all of the bracketed [9] codes.
Then save, merge config and all dialouts will show the number you have supplied.