Orange light above bars every time I call
Disconnected Siri and I still get orange light above bars on phone. Siri randomly called a friend when I was not home.
iPhone 7 Plus, iOS 13
The orange light means the microphone is being used. When you call someone, the microphone is used to transmit your device for the phone call.
Also see the following from Status icons and symbols on your iPhone - Apple Support
An orange indicator 
means the microphone is being used by an app on your iPhone.