If I have a orange dot being in the corner of my phone everytime I’m on a call, does that mean someone is listening through an app ?

It only indicates that the microphone is being used by an app on your phone -- when you are making a call the Phone app is using the microphone. 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.

The orange dot wouldn't indicate that since it is supposed to be on while you are on a call. It is completely normal for it to be on then. If it was on when you weren't on a call and weren't using any other app that uses the microphone then it would be a reason for concern and further investigation.

Phone is an app; when you make a phone call, the Phone app uses the microphone. No one could hear your voice on a phone call if the Phone app didn't use the microphone.

The orange dot turns on when am making a phone call when I look to see which app is requesting the microphone

it’s says phone no apps just says phone.