This is incorrect.
Essentially if we have to route the call outside of the IP level and to the "public network" then the call is billed.
If we are able to peer directly, i.e. with a SIP Address -- think of this much like an "email address", i.e. sip:user@host than the call is free.
So to further clarify -- if you were to call a Vonage phone number via their ten digit phone number the call would not be free.
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