Comment by lozf

You might like FreePBX[0] for a PFSense-style "PBX appliance" with easy WebUI. Just grab the ISO (or shell script to install on Debian). It's built on Asterisk, and more than adequate for the task. Whilst FreeSWITCH is awesome it's way more complex and overkill for this use case.

[0]: https://freepbx.org