In order to launch an outbound call you need to use the HTTP API:
http://www.3cx.com/blog/docs/3cx-http-api/
You can configure your CRM to launch the outbound call using that API, and connect it to a VAD callflow (VAD callflows are registered as extensions). Then, you create the VAD callflow to reproduce the prompt you want. To do that, you only need to use a Prompt Playback component.