I have a Nexus 6P running the latest version of Android 6.0.1. I am not sure if this issue is for all Android Users of this version of specifically a Nexus 6P bug. I never experienced this issue with my Nexus 6. If I say 'OK Google' and then 'Call Persons Name' it used to instantly calling them. Now the phone gets confused on 80% of my contacts. On the screen it says calling via Google Voice and the call always ends up failing. UPDATE: I figured out why it keeps trying to call via Google Voice. This is because Google Now keeps putting a + before the persons phone number as if it is going to be an international call. Then the call fails. I do have the Google Voice app on my phone for Visual Voicemail use, but have the setting 'Do not make any calls with Google Voice' in the settings.