As you can see from all the replies, including from Bill Simon himself, this isn't complicated; it's just a few basic values to enter on a form. If you have entered those values correctly, then it should simply work.
This week, I fixed another user's issue that was similar to this one, but with a different SIP service provider. It turned out that there was some sort of left-over configuration junk in his OBi that was interfering with trying to configure the new SIP SP information.
I suggest doing this:
Log onto the OBiTALK web portal. Delete the OBi completely off of the portal. Wait a few minutes while the portal remotely reboots the device. Unplug the power and Ethernet cables. Plug in just the power cable and let it boot up. Then, key in ***8 then 1 to reset it to factory defaults. After it gyrates and reboots a couple of times and the LEDs become stable, plug in the Ethernet cable, and use the **5 procedure to add it back to the portal, skip the invitation to set up Google Voice, and scroll down to the bottom of the page. Click the "OBiTALK Compatible Service Providers" link. On the next page, enter your SIP information, and see if it works.