Got this little iPhone 4s from a friend more than a year ago. After I set it up with my own Apple ID, the same I use on my main phone with my SIM, someone called me, and it also rang on the 4s. I was very surprised, because I though only the 5c and above were capable of this feature. However, it never happened again, not even with the same person who called at that time. As you can see, the phone says “Nincs SIM” in the top left corner, which means “No SIM” and “az iPhone-járól” means “from your iPhone”, so this was probably a WiFi call. Still confused about this.