I work In a Company that is a Nethesis Partner, so we sell/maintain Nethserver Ent to our customers (file server, mail server, base for other Company software, firewall, PBX) and use it internally.
I installed a Nethserver NG 6.9 Ent with Nethvoice at home and, with a list (tellows) and a script I can block most of the unwanted calls (mom thanks!).
Then I have installed a VM inside with Nethservice NG 7.4 with Madsonic.