The Apple iPhone 5s Charge Port Flex Cable (includes Headphone Cable with Mic) is composed of three separate parts located at the bottom of your device under the screen. Your headphones plug into a jack that is on this flex cable as well. If when you call someone, you can hear them, but they can’t hear you, then you need to replace the microphone which is also part of this flex cable. This flex cable for the iPhone 5 also contains a chip that allows your device to sync with a data cable. If you are getting error messages when you try to connect to iTunes, then you may need to replace this part.