[jeroenhd]

I haven't tried it myself (I don't even run an XMPP server anymore) but based on the description, combining something like sylkserver[1], perhaps with a dedicated SIP service (Asterisk/FreePBX?), should get you VoIP phone calls from XMPP. You can probably get one of those SIM-to-SIP devices (or maybe there's software) if you want mobile phone calls.

There's one problem with this setup: emergency numbers may not work and might get routed to the wrong place.

[1]: https://github.com/AGProjects/sylkserver

[prmoustache]

There is another major problem which is latency. I hate it when someone decides to call me using whatsapp by convenience (the phone/call button is easy to reach right on top of the message view) because latency is way too high which means people keep speaking at the same time unless you use it like a walkie-talkie and say "over" when you clean the line.

I know the latency is already a thing with regular wireless phone network and we will probably never get back to analog wired level but it is still much lower than the latency the instant messaging apps call have, which is just too much to be bearable for anything else but the very occasional call.

[bryant]

> which is just too much to be bearable for anything else but the very occasional call.

I've compensated for this in IM calls by speaking with a more deliberate and measured cadence as well as adding slightly longer pauses (and waiting for such) at transitions in conversation. At least for me, it's worked just fine.

I have plenty of friends on the opposite side of the planet who I can carry a conversation with despite the latency by following this.