Red dot appears on my Iphonexr when I answer calls disappears when I end the call

If you are referring to a dot in the area of the battery icon, that is a notification that the microphone is being used. It would have to be for a phone call. See this for an explanation. About the orange and green indicators in your iPhone status bar - Apple Support

Understand that depending on your wallpaper, the orange dot can appear reddish in color.