Q: The microphone of my iphone6 barely works when I talk on the phone.  It is not dusty, nor is it covered with plastic or anything else.  I tried turning off bluetooth and turning off Siri.  It worked fine for months, but now I can't use the phone.

Hello sigmurph, 

Thanks for visiting Apple Support Communities. 

It seems like you can't be heard when making calls on your iPhone unless you put your mouth right next to the microphone. 

You've tried some good steps to isolate the issue. Next, try the test and the troubleshooting steps mentioned in this article: 

If your voice is too faint or sounds unclear using iPhone, or iPod touch - Apple Support

If you can't hear your voice clearly when recording a voice memo, and the troubleshooting steps in that article don't help, you may need to contact Apple Support using the link in the article:

If you've tried these steps and people still can't hear you well on calls, contact Apple Support.

Best Regards,

Jeremy