LG G3100 User Manual page 167

You can reject an incoming call without answering by simply
pressing the [End] key.
When in a call you can reject an incoming call (1st call) by pressing
the [Menu] key and selecting or by
pressing [End] key.
You can control the volume during a call by pressing [Options] key
followed by U or D .
and selecting
You can mute the microphone during a call by pressing the
[Options] key then selecting . The handset can be unmuted by
pressing the [Unmute].
When the handset is muted, the caller cannot hear you, but you can
still hear them.
To turn DTMF tones on during a call, for example, to allow your
handset to make use of an automated switchboard, select the
[Options] key, then . DTMF tones can be turned off the
same way.
The Messages and SIM Tool kit main menu options can be reached
from the in-call menu by selecting the [Options] key, then
(Screen name depends on the network operator's
SIM). SIM Tool kit menu is shown only when SIM in the handset
supports SIM Tool kit service.
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