That’s all great except I have a “pre-anncouncement” IE: Nobody is available to answer your call, then another anoucement that changes periodically. So I need both setup. The extensions_override fixed it for me.
cat << 'EOL' >/etc/asterisk/extensions_override_freepbx.conf
[app-vmblast]
include => app-vmblast-custom
exten => vmblast,1(digits),ExecIf($["${DIGITS}" != “”],SayDigits,${DIGITS})
exten => vmblast,n(msg),ExecIf($["${VMBMSG}" != “”],Background,${VMBMSG})
exten => vmblast,n,VoiceMail(${GRPLIST:1},s)
exten => 1,n,Hangup
; end of [app-vmblast]
EOL