I haven't had my Obi long, and don't remember ever setting up call forwarding. Someone who was trying to call my Obi number instead was forwarded to my cell phone. This person has both the obi (home) and my cell phone number programmed into their phone. When I call the Obi number it works fine and doesn't forward my call. I've looked online and it looks like I don't have any call forwarding set up. Thanks!
Sign back into your Google Voice account Settings, scroll down to "Linked numbers" and see if your cell phone number is there. And delete it. Have that someone call direct to your Google Voice phone number. Incoming call should only ring phone plugged into the OBi device now.
Good luck!