I've got Gmail and Google Voice. My Google Voice is essentially an alias for my cell phone. Here's the problem though: if I happen to have Gmail open in a tab on my computer, and a call comes into my cell phone (on the real cell phone number, not the Google voice one!), Gmail will display that there's an incoming call (and make an obnoxious alert noise) in the little "Hangouts" widget on the left, but my cell phone will not ring. There will be no way to answer the call at all on my phone.
I want to answer phone calls on my phone, not on a computer! How do I prevent this from happening and ensure that incoming calls always go to my phone, regardless of whether I have Gmail open?