LG G3100 User Manual page 173

You should speak a word within 2 seconds, and the phone asks you
to speak it again to ensure the accuracy of voice recognition. After
voice recognition has finished, Voice is attached automatically.
• The voice can only be attached to main number which you
set. For example, If you change main number voice will be
automatically attached changed number.
• You can add voice tag to phone number in SIM card.
The voice tag can be erased removing or changing SIM card.
And voice tag attached to phone number in SIM card may be
attached to another phone number when you changed SIM
card. Why? The answer is that SIM card doesn't contain
information about voice tag.
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