I'm using a Nexus 6 and having constant call drops.
I'm on a Nexus 6. The phone service seems to drop constantly. Sometimes it will go 5 minutes, sometimes 20, but the calls always go silent. They don't disconnect completely unless the other person hangs up. This happens on 4G and Wifi. I've tried lowering the quality of my calls, I've changed every setting imaginable for codecs and quality. It still happens. I even tried dialing *#*#72786#*#* as the troubleshooting app suggests. This results in endless ringing. Nothing resets and the phone doesn't restart. I'm also not receiving calls. The phone doesn't ring and callers are sent directly to voicemail.