To truly clean out the GV configuration and start over, with no doubt that you have leftover artifacts from GV causing problems, you can simply reset the device.
Log onto Obitalk and delete the device off of your list of devices (otherwise, Obitalk may try to overwrite the confguration).
Look for the little reset hole in the back of the box. With the power on, insert tip of a paper-clip and press for 10 seconds. The power LED will blink and the unit will reboot.
Now, add the device back onto the Obitalk portal, as if you just purchased it. Then, configure it for Callcentric. You don't need to use Expert configuration for this, unless you want to modify any advanced settings. Yes, the portal will remotely reboot the device any time it needs to do so to effect a change. It may take a minute for the remote reboot to be initiated.