Ensure that your administrator has enabled ringtone customization.
Ensure that the Presence incoming call indication or Presence parked call indication is set to Audible or Both.
Procedure
Press Main menu.
Scroll to Settings, and press Select.
Scroll to Audio, and press Select.
Scroll to Personalize ringing, and press Select.
Scroll to one of the following, and press Select:
Presence incoming call
Presence parked call
Scroll to a suitable ringtone, and press Select.
Press Save.
Result
The system saves your selected ringtone.
Note:
If enabled by your administrator, the phone locally saves your adjusted ringtone volume level. You do not need to readjust your volume after the phone restarts.