This number without a caller ID name called my mobile line twice in rapid succession on the morning of April 26, 2016. I didn't answer, and they left no message either time.
Called on personal cell while I was at work. No message left. Caller ID says Oklahoma. Um, don't know anyone in Oklahoma, don't want to know anyone in Oklahoma. Been there once. *shudder* Blocked
This number without a caller ID name called my mobile line twice in rapid succession on the morning of April 26, 2016. I didn't answer, and they left no message either time.
TL;DR - 313-438-8407 isn't really associated with the (possibly spoofed) 405-417-2388 nuisance calls. 313-438-8407 is just part of Google Voice's call handling network.
I think you're misinterpreting what you saw. That "actual" number you listed, 1-313-438-8407, is part of Google Voice's network. The reverse lookup directories I checked list Google Voice as the carrier for that number. When you use a GV app to make an outgoing call, the app uses whatever phone you're using to call a number on GV's network, which then forwards the call to whatever number you dialed. This way, the person you called gets your GV caller ID info instead of the caller ID from whatever phone you used to place the call, and any special charges (like international rates) are billed to your GV account instead of your regular carrier. The app integrates pretty well with the phone's call log and contact list (at least on Android,) so it's easy to miss what's really going on behind the scenes with GV.
My "mobile number," the one I tell people, is really a Google Voice number I use to forward calls to and from whatever mobile handset/SIM I happen to be using lately - saves me the trouble of porting numbers with carriers. I use the Google Voice Android app on my mobile handsets, which are set to place calls through the GV app. When I check call details from my mobile carrier(s,) all of my outgoing calls are to a handful unfamiliar numbers. But they all correspond to times when I made calls to people I know. Those raw calls are where the app is handling my outgoing calls through Google Voice; my carrier sees only the first leg to the GV network.