Cathy is going to Italy and wonders if Viber will be good for getting free phone calls. Leo says that Viber is like Skype in that it uses the internet to make a phone call. She can also use Facebook Messenger. The issue is that whoever she calls will have to use the same program on the other end, unless she spends money to allow it to make calls to any phone. She'll want to be sure she doesn't use her carrier's data while being out of the country. It'll cost her thousands. She can use Wi-Fi, though.
She should turn off data roaming in her phone and it will never allow her to get on the international data networks. She could buy an international data roaming plan, or even go to prepaidwithdata.wikia.com and see where she can buy a local SIM card. She'll have a local number but she can get her data that way and save a lot.