Cisco 8865 Series Manual page 17

Adjust the Volume During a Call:
If the sound in your handset, headset, or speakerphone is too loud or too soft, you can change the
volume while you are listening to the other person. When you change the volume during a call, the
change only affects the speaker you're using at the time. For example, if you adjust the volume while
you're using a headset, the handset volume doesn't change.
Procedure
Press Volume up and down to adjust volume while you are on a call.
Adjust the Phone Ringer Volume
If your phone ringer is too loud or too soft when you get an incoming call, you can change the ringer
volume. Changes to the ringer volume do not affect the call volume you hear when you are on a call.
Procedure
Press Volume up and down to adjust the ringer volume when the phone rings.