Callwithus over VPN attainable

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Hello of people,
I found the Voip offerer Callwithus.com coincidental, to that among other things an entrance over VPN offers. Certainly costs the which unfortunately.

White someone of an offerer in this country (e.g. Beta max or other one), which also a VPN as entrance offers? As free of charge as possible….

Or other question:
Did it create someone to furnish a VPN for sip over two Fritzen?

Thus Fritz1 with telephone at distant place and Fritz2 at home, which develop then a connection to the Voipprovider?
Everything without current PC.
Goes sowas in principle?

Greeting frame.