Q: My Siri and voice message won't work on my iPhone 6 how can I fix it?

Greetings Bribri2168,

Welcome to the Apple Support Communities!

From your question, it sounds like the issue you may be experiencing is with the microphone on your iPhone because of both features you mentioned. To begin troubleshooting, please read over and work through the steps outlined in the attached article below.

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

If this is not the issue, can you please explain to me in further detail what alerts or errors or failures you receive when you try to use Siri or record a voice message in Messages? 

Cheers