Hi:
You don't "port a number to Obihai". You port a number to a VoIP telephone carrier, and then you configure your OBi hardware device to work with your new carrier. Examples are listed on Obihai's main page, and their service provider list, when you go through the setup procedure (for example, Callcentric,
voip.ms, etc.). Note: you can't port a land line (FiOS for example) directly into Google Voice; you'd need to first port it into a prepaid mobile carrier, such as GoPhone, and then wait a week or so for the carrier databases to be updated. This would be at your own risk, as there is no guarantee that any particular number can be ported into GV.
On the other hand, unrelated to Obihai, have you looked into
nomorobo.com? It's a free service, and it was the winner of the FCC's contest to develop robo-call blocking solutions. You would need to subscribe to simultaneous ringing service from Verizon. When someone calls your phone number, it also rings a number at nomorobo. They have a database of known spammers, and when a robo-caller ID is calling, they'll answer and dump the call.
This also works with Callcentric, although it's not documented on nomorobo's website. You just have to lie to the nomorobo setup routine, and tell it you are using a supported carrier (Vonage).
Since I started using nomorobo, the only junk calls I get are from charities or political callers, which, by law, aren't considered covered under the "do not call list".