If it was me, I would buy a new number with a company like Voip.Ms
(40 cents onetime charge to get a number and 80 cents a month base rate on the pay per minute plan).
I'd set up my white list and/or time of day filter and/or set up an Attendant "Press 1 to".
Then I'd add the new account to my Obi (or Obi phone) to receive all calls. I would be paying perhaps a cent per minute for any calls that I received, but could still use GoogleVoice for free outbound calls.
I would then forward the GV number to the new number.
It is slightly more work to set this up but can eliminate lots of bogus calls.
A setup might be:
A call comes in and the whitelist is checked. If the number is allowed, then ring the phone.
Then if the caller is NOT in the white list, the time of day is checked. If daytime, pass the call through to the phone. Otherwise send it to voicemail.
That way you automatically 24 hours a day get calls from certain people, then the rest are only allowed during the day because they might be a doctors office, etc.