It looks like a rebranded OpenVBX which runs off of Twilio. If anyone has an account, it'd be easy to check... search for an available number in TellFi for a given area code and also do the same search in Twilio. If you find the same number in both places, there's your answer.
You think Twilio owns all of those phone numbers? They are most likely just using another API as well.
It's not. We built this from the ground-up.
Can you talk at all about your infrastructure then? Is it powered by asterisks, FREEswitch, something else, ?