Tap the speaker icon on the top right of the screen,
then select the volume control options, or adjust the
volume of the incoming call sound.
Alternatively, you may use the volume control key on the
side of your GPS Phone 600 by pushing it up or down to
control the volume.
If you still do not hear any sounds select the
Start Menu -> Settings -> Sounds and Notifications -> and make sure
that the first 3 boxes for “enable sounds for?Events, Programs, and
Notifications are ALL checked
on the top right of the screen,
then select the volume control options, or adjust the
volume of the incoming call sound. 
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