Wifi or cell network?

Question

I have Google Voice on my PC linked to my Android phone, which has a prepaid plan without data.  When I'm at home and receive an incoming call, it rings on both the  phone and the PC.  If I answer on the phone, I assume it connects by wifi.  Is that so?  If I'm on the street, I might (or might not) be in range of NYC's public wifi.  How can I tell if calls sent and received on the street are using wifi (free) or my cell plan (10¢/min)?

Bluescat · Accepted Answer

Understand that Google Voice has two ways of working:  the old way, which forwarded calls to regular telephone numbers over the telephone network, and the new way, which uses Voice over IP (VoIP) Internet calling.  VoIP calls do not go over the carrier telephone network, so they are not using any of your cell phone plan minutes.
 
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Question #1:  if I answer on the phone, is the connection by internet/wifi (free) or through my carrier (10c/min)?
 
This depends on how you are using the app, either via the carrier method or via the VoIP method.  This is a setting in the app, "Making and receiving calls".  The two choices are "Prefer Wi-Fi and mobile data" and "Use carrier only".  Ordinarily, people with Android phones have a data plan, so they'd leave that setting as "Prefer Wi-Fi and mobile data", which would work at home on Wifi and away on 4G/5G data.
 
The "use carrier only" method actually still needs to use a very small amount of data to set up the call, and then the call itself uses your carrier.  Since your phone has NO data service, the calls will all fail, and you can't use the Google Voice app at all when you are out of WiFi range.
 
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Question#2: I've received incoming calls to my Voice number when I was on the street.  If there was no internet connection, obviously the call must have come through my carrier.  But what if the phone was connected to the Internet through NYC's public wifi? 
 
Again, this depends on the app's settings.  Assuming you have set the app to "Prefer Wi-Fi and mobile data", it will do just that:  PREFER Wi-Fi and mobile data, if available.  Otherwise, it defaults to forwarding the call over your carrier number.
 
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Question#3: If I change the Android settings to deny permission for Voice to access the phone, will I still be able to make and receive calls when the phone is connected to the Internet by wifi?  
 
No.  That won't work.  Don't do that.