Using the Google Voice app is the way to go, when you set it up remember to select "Ask every time" or "Use every time" and when you enter a number or dial from your contact directory, it must have all 10 digits or the GV app won't route the call, even on a local call...
Google Voice turned on:
Dial 222-1234 - Goes out via carrier
Dial 202-222-1234 - Goes out via Google Voice
For some reason people just don't seem to get that sometimes.
Current Personal Phone: Google Nexus 4 (KitKat 4.4.2 KOT49H/AT&T GoPhone SIM)
Current Work Phone: HTC Rezound on VZW (S-OFF/LiquidSmooth
Current Tablet: iPad 4 and Nextbook 8 Premium with marxo's N8+ ROM - Revision 1b2 (ICS 4.0.4)
Previous/Retired Android Devices: HTC Aria, HTC Incredible 2, Samsung Stratosphere, HTC Rezound, Samsung Galaxy S2 Skyrocket