I was considering Fongo for our apartment and I had some questions/concerns. I also pointed out some issues with Fongo's website and account page.
The support I received was cryptic and bot like. It was unclear and I followed-up requesting additional information. Fongo chose to remain silent including issues regarding my Account.
As a free service (their mobile app), Fongo is ok (not great) but to use Fongo VoIP services as a primary phone line, my experience says no. I don't recommend Fongo.