Well I'm not going to name specific companies, but you know those international calling cards that are sold basically everywhere in areas with a large migrant work force? Those cards tend to use these discount VOIP networks.

I assumed WhatsApp audio and FaceTime audio killed that market years ago.

You might also assume Vonage was killed off, as I did until recently discovering they have a multi-billion market cap.

Vonage is supported by people like my parents, who for years have used the landline via Vonage for at most 2 phone calls per month that could have been done via a multitude of apps, yet refuse to heed my advice to cancel it.

Try setting up E911 service for a GVoice voip phone in your house sometime -- you'll run across a lot of web UIs that look >10 years old.