If there is any background noise then the phone may not pick your voice up correctly.
Here is a link to the manual: http://www.lg.com/us/support-mobile/lg-LG306G#
Ok, that is very strange!
Try un-pairing the H730 from the phone, then pair it again..
Let me know if there is any improvement?
Have you tested the H730 with any other phones?
Ok, let me know if I can be of any further assistance at all.