VoIP is the protocol used to carry the audio part of your phone call. Almost all VoIP providers route the data to a call center where it is interfaced into the regular phone system if the number you are calling is a standard landline phone.

I have a VOIP phone (broadvoice.) I haven’t found a phone yet that I cannot call, nor a phone that cannot call me. When I use certain VPN services, outgoing calls are blocked, though.

Of course you can.