In syncing up my Google Voice account with my Sprint phone account, I've had a blast being able to text people when my phone is dead from my computer, and having records of everything that is in a conversation so I don't miss anything.

When I try to call someone, as you know, it brings up the following options:

1. GV Direct Dial
2. GV Call Back
3. GV Offline Dial
4. Carrier

My question is: What do the three types of GV dialing do? Do any of them allow me to use WiFi to connect calls as opposed to Sprint service? I signed up for a Google Voice account for the ease of accessing text messages, and because I was under the impression that WiFi phone calling was available when I have access to WiFi but not Sprint phone service, since their networks aren't as widespread and available as Verizon's.

Thanks!