My MIC doesn't work... It does for phone calls, until I go on speaker phone, then nothing. It also doesn't work for Cortana or videos... Any help would be appreciated.
Are you talking about the headphone/mic port along the top of the phone, or are you talking about the internal mic, built into the mouthpiece? Because from the sound of it, the original question was about the internal mic.
Mine has the same problem. Works fine when I hold the phone up to my head (no bluetooth, no plugged in headset, just talking on the phone, with the phone up to my head like normal), and am talking on the phone. But the moment I put the phone on speaker, or attempt use Cortana, I get nothing. If that is a known warranty issue, I am sending mine back into Nokia (not T-Mobile, who will only send my someone else's refurb) this week.