There is another option, but I don't think it's worth much: you can open a free account at Gizmo5 and set it up to make free calls using Google Voice with your SIP phone or ATA. The catch: the calls are limited to three minutes.

Otherwise, you could set up a speed dial setting on your phone rather than on vPanel (assuming your phone supports it) that would get you most of the way there, so that you hit the speed dial number and then input the telephone number.

But to what end? You already have "unlimited" outbound calling from VOIPo. Are you just trying to have your CID show the GV number rather than the VOIPo number? If so, perhaps we should request CID spoofing as a feature. Other providers offer it.