[michael_michael]

I've built my own business VoIP system — a few times over. I've used Asterisk and FreePBX (the free-ish GUI built on Asterisk), but settled on Asterisk for stability. At one point FreePBX pushed out an update that took down my system for a couple of days and baffled me until I read the FreePBX forums and saw similar complaints from other users.

If you want a week-ish long project, go for the full mid-2000s, boingboing and slashdot experience: buy the dead tree version of the O'Reilly Asterisk book, which has been kept up to date and is still an wonderful resource. Follow it until you have the Enterprise-grade phone system of your dreams.

I even hired Allison "The Voice of Asterisk" [0] to do our phone tree voice prompts. Her prices were very reasonable for a small batch of prompts, and it’s surreal hearing the same lady that does the IVR for your bank and cable company do your own voice prompts.

I use Twilio for my SIP trunking, and it has nice fallback features in case the Asterisk system needs to go down for maintenance or the like. Costs about $20/month for a dozen or so users and fairly frequent calls/SMS.

[0]: https://www.theivrvoice.com/