My Verizon contract has 1400 minutes shared with 3 cell phones. I noticed that my cell number was using minutes from the calling plan. I normally call the other two cell phones, and my home number (which is on my friends of family calling list). My original intention was to be able to hide behind Google Voice and not allow my cell phone number to be broadcast. Google Voice would use whatever phone number was available on their server, make the call, then connect with my cell phone to complete the connection. I didn't notice that my minutes were being used until after someone else reported that they had exceeded their plan minutes after switching their cell phone to use their Google Voice number for outgoing calls.
I called Verizon concerning this issue, and their only response was to contact the third party.
I have now, and informed my friends, to only use their number and change the Google Voice APP, Making Calls setting to "Do not use Google Voice to make any calls".