Fixline is an application that makes phone calls over WiFi for free. It is based on WiFi calling, which allows you to make free calls over a WiFi connection with your smartphone. The application does not require a phone number or be shown to others. Thus, it's a safe option.
It also allows you to make calls to people in other countries, even if they do not have the app.

It is the best solution for those who want to stay in touch with their family and friends, regardless of where they are in the world.