When I purchased my Moto X In MArch I found that I had poor coverage in my area so I looked into Sprint Wifi. Sprint says that only the Samsung galaxy phones can use the wifi option. Do not talk to Sprint. I found that Sprint wifi uses Google Voice. So I went to the Google Play Store and downloaded Google voice. I didn't know that there was a link to to Sprint wifi until I started to do the set up. I chose to use MY cell phone number instead of the google voice number. after that I saw a link for Sprint wifi. I tapped on it and it set up the wifi calling. If you have had Google voice on you phone for a long time then you may not have the link. I suggest that you uninstall it and download it again and use your phones number instead of the google number. My phone is clear and loud as long as no one is surfing. this is a great option for areas of poor reception! I hope that this helps.
Okay, it seems that we can make outgoing calls using WiFi which is great. What I haven't seen yet is, when overseas in a qualifying country, can I get a call while using WiFi as long as I'm connected to a WiFi network?