How to make a call from a PC through your smartphone?

Question

Asterisk

Let's say that I live in country A and my brother lives in country B. I have an Android smartphone with free calls in my country. My brother also wants to call the numbers of my country from his completely free of charge. What are the options for him to make calls through my phone?
As far as I know, there are some solutions to this problem, such as Asterisk and FreeSWITCH, which can be installed on your server and they can redirect calls to different devices connected to them. Then my brother will be able to install a SIP client on his computer and call from my Asterisk server through my smartphone. But these solutions are quite complicated to set up (you need to read a bunch of documentation and edit the config files).
Are there any easier ways (also free) in order to implement our plans? Or who will suggest how to quickly configure Asterisk / FreeSWITCH for my needs.
The server is. GSM modem / phone costs a penny, you can buy and connect to the server.

Answer 1

If the case takes place in Russia, then Megafon has a certain Multifon

Answer 2

Oktell GSM GateWay + FusionPBX = quite simply
even simpler Oktell GSM GateWay + Sipuni - but you have to pay a little there