audio antes de llamar call center ...

 https://forum.issabel.org/d/3008-reproducir-primero-audio-antes-de-sacar-llamada

I don't think you can do it using the GUI, but you can do it through dialplan.

INSTRUCTIONS
1> Find the outbound route you want that message played.

My outbound route name = "international"

2> In "SYSTEM RECORDINGS", create the recording that you would want played.

example "Warning International call being made"

save as "internationalwarning"

3> open /etc/asterisk/extensions_additional.conf

Find your outbound route in this dialplan. Below is an EXAMPLE of what mine looked like.
Yours will be similar, " [OUTRT-XX]; NAME " will be different as will some of the phone numbers.

My example, calls that start with 011 as the number that is called that uses this trunk.

------ example ---------------

[outrt-1] ; international
include => outrt-1-custom
exten => _011.,1,Macro(user-callerid,LIMIT,EXTERNAL,)
exten => _011.,n,Set(MOHCLASS=${IF($["${MOHCLASS}"=""]?default:${MOHCLASS})})
exten => _011.,n,Set(_NODEST=)
exten => _011.,n,Gosub(sub-record-check,s,1(out,${EXTEN},))
exten => _011.,n,Macro(dialout-trunk,2,${EXTEN:3},,off)
exten => _011.,n,Macro(outisbusy,)
;--== end of [outrt-1] ==--;

----- END EXAMPLE ---------------

4> COPY the entire code piece

5> OPEN /etc/asterisk/extensions_override_issabel.conf

PASTE the code into the bottom of this file.

6> You will need to insert a custom code in to play the recorded message.

Put the next line in 2 locations

exten => _011.,n,Playback(./custom/internationalwarning)

My dialplan example uses _011. Yours might be different so you will need to adjust it accordingly

[outrt-1] ; international
include => outrt-1-custom
exten => _011.,1,Macro(user-callerid,LIMIT,EXTERNAL,)
exten => _011.,n,Playback(./custom/internationalwarning)
exten => _011.,n,Set(MOHCLASS=${IF($["${MOHCLASS}"=""]?default:${MOHCLASS})})
exten => _011.,n,Set(_NODEST=)
exten => _011.,n,Gosub(sub-record-check,s,1(out,${EXTEN},))
exten => _011.,n,Macro(dialout-trunk,2,${EXTEN:3},,off)
exten => _011.,n,Playback(./custom/internationalwarning)
exten => _011.,n,Macro(outisbusy,)
;--== end of [outrt-1] ==--;

Save your changes

7> reload the config in asterisk CLI ( asterisk -cvvr then core reload)

TEST!

What will happen is, when asterisk goes to dial the code, it will run this custom code, play the message then continue the dialing.