But either way, be sure to back up your data as it will be wiped during the process. I would recommend the second way as it is a more complete reset which installs a fresh version of the OS as opposed to using the files that already exist on the phone. This can either be done either in the settings menu or by putting your phone into dfu mode and connecting it to a computer with itunes installed. However, if people are able to hear you while using speakerphone then I would try a factory reset. That microphone is located on the same flex cable as the front facing camera and proximity sensor. However, with iOS 11. FaceTime isnt available or may not appear on devices purchased in Saudi Arabia, Pakistan and United Arab Emirates, including Dubai. You may have issues using FaceTime for one of these reasons: FaceTime and FaceTime audio calling may not be available for all countries, regions or carriers. If people are not able to hear you then you will most likely need to replace the microphone near the earpiece. Over Wi-Fi, FaceTime requires a broadband connection.

First try putting the phone on speakerphone when making a call.

The 5C has two microphones one located at the bottom (used when making regular phone calls) and one up near the earpiece (used for facetime and speakerphone).

Facetime without wifi