Is free VoIP a scam?

VoIP Expectations

No. In almost all cases, calls between users of a service are free. These are called Network Calls, In-Network Calls, or User-to-User calls. Skype is particularly well-known for these calls. Calls to the PSTN are never free – the VoIP provider actually has to pay something to the phone network that the call terminates with. Google Voice is the only VoIP provider that allows free calls to the PSTN in the United States, but these free calls may not last very long and they do cost Google some money.