Hey,
I am Abraham, Senior VoIP engineer and consultant with robust and extensive Asterisk experiences as well as all forks including freepbx.
I've done dozens of custom dial-plan and functions on asterisk and freepbx so far, and this setup is very clear for me.
I'll get you a solid and reliable setup that works like a charm.
It will be a custom dialplan that dial your pager and send dtmf once answered and prompts is done.
Please read more on my profile about me and reach me for further discussion.
Kindest Regards.