iPhone 32GB (black) 4S with Sprint. I’ve noticed this same issue since I got the phone on 10/14 via pre-order process. The echo sneaks in intermittently sometimes 1, 6, 18 minutes or 1 hour into the call. Doesn't matter if the person I'm chatting with is from ATT or Verizon. The volume of the call goes up and the caller gets loud echo on their side. The call quality becomes unbearable! The conversation is ultimately short-lived especially as you have to keep calling back. I’ve never had this issue on the Blackberry I had before which really narrows down the problem to either the iPhone or the sudden change in Sprint’s network.
I have Sprint network team looking into it already. I’ve experienced this every time I use the Apple earphone unit to take and make calls. Apple store Genius support indicates that it is not due to hardware as I am able to listen to music just fine without the echo. They also state that if it was hardware related, that the experience would be more consistent and exact in time of occurance. I’ve been back and forth whether or not I should return the phone but it looks like some of the folks experience the same issue, hence a replacement for another 4S may not be the best way to resolve the issue.
It may be a long shot, but this may be due to the SIRI mode of being enabled when placing the phone next to your ear. This feature is defaulted “ON”. Perhaps turning this feature off and just enabling SIRI when pressing the iPhone button will fix the echo problem??
The preference can be toggled under General->SIRI->Raise To Speak. Hope this is the issue that will resolve the echo problem we’re all having on our calls!
Good luck everyone!