I am tired of paying for roaming, of being location tracked by my provider and running out of SIM slots.

So I have decided to connect some SIM capabilities to my server and set it up as a sort of proxy that I could access over the internet to send regular SMS and make regular calls through the server.

As far as I can tell it seems to be really complicated to do in linux and I just couldn't find anyway that would actually support sound over calls.

The only solutions I found right now are to get an old phone (not ideal because of the price, battery and reliability) or use something like

https://www.makerfabs.com/maduino-zero-4g-lte-sim7600.html

Which can be connected to the server on the aux and serial ports. This is not too pricey but still seems like a bit much for my needs.

My question is, are there better ways? Really all I need is SMS and calls.