LG G3100 User Manual page 200

The currently displayed caller of a multiparty call can be
disconnected by pressing the [End] key. To end a multiparty call,
press the [Options] key then select multiparty.
Selecting the [Options] key then , will end all the
active and held calls.
If you have one caller on hold and another active call, you may
connect one call party to another call party and then leave the call.
This is done by selecting the option from the in-
call menu.
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