Why does my device beep when I'm talking to someone?

You may be hearing the Call Waiting tone. Check the name that is flashing on the display. If it is not the name of the person to whom you are speaking, it means that someone else is trying to call you. The display is flashing the name of that caller.

If there is not another call waiting the device beeps. For information to determine why your device is beeping, refer to Why is my device chirping or beeping?.