Change default ringtone for incoming calls by navigating to “Settings” -> “Personalization” -> “Sound” -> “Tones” -> “Ringtones” -> Select a ringtone.
Change the volume for incoming calls by navigating to
“Settings” -> “Personalization” -> “Sound” -> “Volume” -> “Ringtones & Alerts”
You will see a Volume Bar. Press left and right key to adjust the volume.