I got an iPhone X through my carrier (Fido, Canada) Dec. 10 and immediately had problems with it as a phone: people complaining they can’t hear me clearly. I tested the mic and it works A-OK with all other apps (including Voice Memo, Facetime). I sound clear to others in Phone feature when switched to speakerphone – only muffled in Phone app, and only when I switch off speakerphone. I consulted Apple Support, diagnosed+reformatted the phone with an Apple Store Genius, deleting my backup and running only basic config and latest iOS 11.2.1, tried everything suggested by support, from checking mic for debris / case blockage, to resetting network settings, enabling/disabling LTE voice and background noise filter. Over 2 weeks + dozens of hours troubleshooting. I finally convinced my carrier to exchange the phone as defective, but I’m having the same problem with Phone X #2. Apple urgently needs to review the Phone feature app. It’s clearly a software problem + I see in forums online I’m not the only one, and it’s not restricted to the X – some users of the 8 are reporting the same issue.