I have a Moto G3 phone. I'm traveling to Iceland and Ireland for almost 3 weeks. I understand the networks in Europe operate on a system incompatible with North American phones. I will be calling back to Canada frequently. I'll have wi-fi coverage much of the time. My questions: Do I need to buy a SIM card and, if so, is it to make local calls while I'm abroad? Do I need to worry about unlocking my phone? What add-on(s) do I need? Which programs allow me to utilize wi-fi to make calls home and can I call a landline or only another cell phone that has the same program on it as mine? I've seen answers to some of this but don't understand the bigger picture. Any assistance greatly accepted. Thanks!