Is VoIP a service from ISP’s or can I just buy VoIP router and make a virtual number from the router using dsl?

I live in austrailia and i want me and my family to call each other whenever for free using voip. how can i do this? i don’t want to use skype or any other ip telephony program just voip.
I was told if i buy the same brand routers here and in lebanon and make virtual numbers then it would work is that true?

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