There were a few threads from '09 and '10 about phones going to "talking mode" but they were for other phone models (LG VX500 & LG Chocolate). People offered advice about how to solve the problem but in most cases did not work for the original poster. In a couple of cases a person claimed to solve their own problem.
However my wife's new LG Octane is now doing it. Further I just ordered one of the same phones online today which I expect to have in a few days. We tried all of the suggestions, adjusting for different menu sequences as best we could, to no avail.
About the only thing that helped was my wife turned speaker to earpiece and then at least it was muffled.
HELLLLLLLP!
Bernie in CT