You can try Roundpin.
We have published it a few days ago, after a lot of testing. It has the features you are interested in and also video conferences, including link-based video conferences for users that don’t have a Roundpin account.
You can install it along with Asterisk and Coturn (STUN server) on a VPS with 1 CPU core and 1 GB RAM or even less. If you connect Asterisk to a SIP account offered by a provider like Telnyx or Localphone (as we explain in our documentation), you can have very cheap calls to any phone number in the world. On Asterisk you can configure an IVR (voice menu), voicemail, queues, music on hold, call recording, number blacklisting, etc. like on any professional PBX.
Roundpin is free and open source software, published under GPL v3.0 and is also gratis. (We plan to accept donations and maybe direct some of them to Asterisk’s development team, since Asterisk is the foundation of the application.)
Roundpin is easy to install. A complete installation implies installing Coturn (as a STUN server), then Asterisk, then Roundpin. We explain in very much detail how to install these 3 components on the documentation pages listed on the official Roundpin web page mentioned above. The guide for installing Asterisk is quite lengthy but you don’t need to follow all the instructions. We present 4 classes of dial plans and you should choose just the dial plan that is closer to your situation and adapt it, if necessary.
On our website we haven’t uploaded screenshots with video conferences in action yet, for privacy reasons. We’ll upload some probably next week.
We plan to add SMS, fax and email capability in the near future. We truly believe Roundpin is a valid self-hosted FOSS alternative to Skype / Zoom.