Red dot on call icon

If you are referring to the indicators that show you when your microphone is being access.. correct, you can't get rid of that because you need your microphone to make a phone call..

If you're on a call and you press Mute, I believe that indicator will turn off

About the orange and green indicators in your iPhone status bar - Apple Support

(note that 'orange' can be actually appear red depending on the background color, iOS will change it to create better contrast)

OR rereading your post, I'm wondering if you are referring to the notification badge that overlays the app icon..

If you go into the phone app and navigate thru all the tabs at the bottom.. is there a missed call that has not been viewed in Recents? or a Voicemail that hasn't bee listened to?