How do you know if your using WiFi calling or your carriers service if both symbols show up on your phone?

Both the signal strength and the WiFi symbols appear on either side of the att icon on the top left side of my iPhone 7+. And the full WiFi connected signal as well. If I make a call am I using WiFi calling? Or att service which has one of 4 bars at current time ? Pretty simple question but when searching Apple their explanation is vague at best. The words “ you can use” are chosen to describe what is possible when the icon appears. It doesn’t say “you are using” this calling option. It says if you see this symbol “you can” use this option. So .... I see both symbols and no option asking which one is like to use so which one is it using ?