Voice privacy
Note: Availability of this feature depends on your arrangement
with your service provider and the network’s ability to support
the feature.
Some service provider’s networks can encrypt the signal
transmitted during a phone call to ensure others are unable
to listen to your conversation. By default, the voice privacy
setting on your phone is set to Off. To turn it on, press
Menu 4-4-1 (Settings - Network services - Voice privacy).
Scroll to On, then press OK.
During a call, if voice privacy is lost, your phone sounds two
short beeps.