The carriers implement Wi-Fi calling in different ways. My carrier has the shortcut available in the quick access panel.
It also has the option in the phone app settings to turn it on&off and to open the wifi settings menu.
If it's normally in the quick settings panel you might try fully open the panel tap the 3 vertical dots in the upper right corner and select button order. Look for it at top and if it's there drag it down into the panel.