1. Sign into Gmail or Google Voice on your computer.
2. Go to Settings there and Disable from Sprint.
3. Logout of Gmail / Google Voice.
4. Now on your cell phone, goto Voice icon app.
5. Tap the 3 vertical dots on the far right hand side for more options.
6. Choose the Settings option.
7. Now at the top under General, the 2nd option is Making Calls, which was likely unavailable before when your number was Enabled with Sprint.
8. Now, you can change the Making Calls option to what it you want.
9. I made mine "Ask every time I make a call."
I hope this helps!
TheBrian8