5.1 lollipop - Unknown status bar icon (Samsung Galaxy S6, Android 5.1.1)

What does the following icon 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.

EDIT 1: 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.

EDIT 2: 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.

EDIT 3: 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.

Answer

In short, it indicates that for the mobile calls the wifi will be used, if there's a good wifi signal.

I have found it there:

This strange new symbol shows your phone’s set up for Wi-Fi calling. It’s a new feature brought in by the UK’s biggest networks to help give you the best call quality. If your phone doesn’t have good reception, like when you’re indoors, it’ll make phone calls using an available Wi-Fi network instead.