I had a brand new iPhone 6, white, 64GB, and the same thing happened to me. Activated it on 26-Dec-2014, and it broke on 29-Dec-2014.
Making a phone call, you couldn't hear anything on the earpiece and they can't hear you on the mic. Switch to speakerphone, and you can hear them, but they can't hear you. Bluetooth worked fine.
Playing music, the sound came out the speaker. Plug in headphones, nothing changes, sound still comes out the speaker. Didn't do any better with Apple headphones. Cleaned out the earphone hole with an air compressor, no difference.
Took it to Apple, they tried "Reset All Settings", but it didn't help. Gave me a replacement immediately, no trouble. Thank you Apple for taking care of this so promptly and professionally! I hope this next one is better.
BTW, we also got another iPhone 6 and an iPhone 6 plus at the same time, and the other 2 are still working fine so far.