Fine, there's a free global database that stored some random unique ID for you. Now say you're in Lisbon connected to some public wifi network, and I'm in Oslo

Fine, there's a free global database that stored some random unique ID for you. Now say you're in Lisbon connected to some public wifi network, and I'm in Oslo connected to my office wifi network. If I press the button to call your unique ID, how does my softphone get yours to ring?