A phone with a WiFi signal icon appears on the status bar (Samsung Galaxy S6, Android 5.1.1)

What does the following icon that looks like a phone with a WiFi signal in my status bar indicate? And how do I remove it? As far as I know, I didn't turn any setting on that triggered it. I can't find the icon online. My first guess was that it was either VoLTE or VoIP or WiFi calling, but I do not have any of these as options on my phone. The icon does not go away unless I turn off WiFi. Below are screenshots of my full home screen and of the open notification panel. The screenshot below is of my phone's "Call Settings". I have no 'Wi-Fi Calling' option. According to guides online, it should come after the 'Vibrate' option. The screenshot below is the results when searching 'Wi-Fi' in settings. No call options come up. --- It definitely is the Wi-Fi Calling icon (even though I do not have it as an option on my phone) -- I tested it now and I can phone my contacts when in flight mode.