Your post is pretty confusing, but what I think you are trying to do (correct me if I am wrong), is that you want to use Google Voice for outbound calls, but route inbound calls through Callcentric?
If so, yes, you can do that. Just add and verify your Callcentric phone number to your Google Voice settings, as a forwarding number, and check-mark it to enable it.
Use the old, "Legacy" Google Voice settings page. Un-check the box to the left of the "OBiTALK Device, to turn off inbound call forwarding to the Google Voice SPx on your device.
See the attached screenshot.
Eventually, these settings will be available on the new Google Voice web settings page.