I just got the Octane two days ago and am absolutely loving everything about it, except the echo problem.
I am guessing the echo could be a result of the caller hearing their own voice, which is coming through the two speakers on the inside of the Octane, which in turn is being picked up by the mic, hence, the caller hears an echo.
I tried to confirm this and found that it does sound like the caller's voice is not only coming through the external speaker on the earpiece, but also through the inside speakers when the phone is closed. This is a terrible design flaw, because the tiny mic hole sits exactly opposite of the left inside speaker. So, when the caller is talking on their end, their voice is actually being picked up by the Octane's mic and causing the echo. If I am correct in my assessment, then this phone is a total dud and needs to be recalled, which would be a shame because this phone rocks in every other way.
The only fix I see that might solve the echo problem is if they can figure out a way to offer a software update that will shut off the inside speakers when you are on a call. I can't believe LG would have overlooked this problem.