I bought the exact phone model as my son, a Nexus 5. I cannot use voice-activated dialing on mine. No matter what you say like "Dial Richard", it will always respond with a 3-digit random number like "014" or "111" and ask if you want to dial that. At first we thought it might be the Bluetooth devices. I use a Motorola earpiece, one of the better ones and he has Sony wireless headphones with Bluetooth. But he tried his headset on my phone and it did the same as mine. It works perfectly on his phone. I can use the "Okay, Google" thing and it will recognize the voice dialing every time, but sometimes it will not dial, but just stays on a screen (like a text app) and display the word "Dialing", even though it never will unless you press a telephone icon near the bottom. This is not the large popup with the green and red buttons you see when it's actually dialing. We are both using AT&T GoPhone service. Can anyone make sense of this?