I just got iPhone 6 last month and since yesterday afternoon I encountered a couple seconds where the phone is irresponsive and I had to restart to make it normal again. After that I couldn't make any call, either a normal phone call or from wifi, it said Call failed, or no sound. I tried everything: Skype, Facetime. There was one time I managed to make the call (after restarting) but the person could not hear my voice.
I opened Voice Memo to check if the microphone is working well but record button is disabled (greyed).
Headphone is practically not working. I plugged in a headset and the volume is still on ringer and the sound is still coming out from speaker.
I tried "reset all settings" and did a "restore" from iTunes but nothing seems to help.
Update since 13-01-2014:
The next day after restoring from iTunes, it was working well again, but then the next day I found out that the same things are happening again, freezing screen after plugging in earphone, microphone and earphone not functioning. This time resetting network settings won't help it.
I'm trying to rollback to iOS 8.0 to see if it will fix the problem. I really prefer to confirm if this is not a hardware issue before bringing to apple store.