I run my own XMPP server, and I can literally call anyone anywhere in the world on the XMPP network. End-to-end encrypted. No phone numbers required. For free.

https://blog.wirelessmoves.com/2020/05/xmpp-voice-and-video-...

So one of the things you can do with Asterisk and Freeswitch on the PSTN network is hook up a Cisco/Linksys SPA122 adapter or use something more recent. If using a VOIP line, some providers in some countries let you control the VOIP line entirely so you can spoof phone numbers to the PSTN network, and as Asterisk/Freeswitch lets you do things like call record and will send the ringing tones (or what ever you choose to play to someone calling your VOIP line) before you answer it, you can also listen to people talking waiting for you to pick up and answer or direct to a voicebox. In effect you can create a voicebox where you never get charged for leaving a message, ideally for covert activities, legal or otherwise, and its done because of the way the channels are handled. Whilst you are playing the dialling tone back to the caller, you have asterisk/freeswitch setup to record the call from the time the tones are played to the caller, only you never answer and the caller can leave whatever message on the PBX because officially according to internation standards a call was never made and thus charged for. I dont know the legality of it, but it seems to be an exploitable weakness in international standards, for covert activity.

There's lots of things you can do with these and Freeswitch also works on a Pi2B.

You'll find some telco providers have just taken Asterisk or Freeswitch and recoded it enough to class it as their own, but you could run an entire phone company in a country on Asterisk/Freeswitch if the HW is powerful enough.

If you look at the Caller ID standards, the EU standard is based on the old dialup v.23 baud rate. https://en.wikipedia.org/wiki/Caller_ID#Operation https://en.wikipedia.org/wiki/ITU_V.23

So if you want to do some HW hacking, you could start with any old modem and turn it into your own SPA122, and once you have done that you could look at taking an ADSL router and turn it into a SPA122 of sorts. These are just devices with some hw capabilities but could do more.

This is guaranteed to give you more privacy because the data stays inside your own VPN. When using any 3rd party infrastructure all packets can be silently duplicated/mirrored to snooped upon by altering setup and teardown, e.g. mitmproxy.

> How is this better than just getting a VoIP line ..

Many countries block this, and even make it illegal for international calls. Both for security and financial reasons. Telecom companies around the world have an understanding with other on interconnection charges. Security reason should be obvious - it is easier to track people and collect metadata on foreign calls if everything happens through your network.

E.g. Many countries even block voice calls through Signal, Skype, WhatsApp etc.

I agree. Only businesses and VoIP hobbyists bother to self-host their PBX. And smaller businesses are often better off using a hosted service. The time money and hassle spent setting this up and maintaining it can buy a lot of calling plan minutes or months. Or you could train your contacts on how to use Signal.

Yes, calling any other EU country from the EU costs a lot. 1 dollar/minute and more. The most expensive plans (50+ dollars a month) usually include 100 EU minutes or so, but not many people have these plans.

Data costs vary a lot across the EU. I pay 70 dollars a month for unlimited data with unlimited speed, for example.

That's not true for over two years. Capped by EU at 19 eurocents a minute. And 70 dollars is pretty expensive, I think you should check if there aren't better deals available (I assume it's CZ?)

https://ec.europa.eu/commission/presscorner/detail/en/MEMO_1...

Within the EU, you will not pay more for being in a different country.

Data and voice may not cost more when roaming

You're right it's cheaper than I said. I didn't check for a few years.

Yeah I get 60gb for 20 euro here in Spain and that's not even on a contract but on prepay. 4gb is measly.