WiFi calling system is another way of making phone calls where we can keep in touch with others through WiFi connection without SIM card through some app or without using any app. This advanced technology can also be used in your Samsung M13.
Samsung M13 comes with Dual SIM functionality, and also you can use the WiFi calling system where you can make phone calls through WiFi apart from the cellular network. But before doing this, you must enable the WiFi calling system from phone settings.