You can use VPN to access Google Voice site, but I don't know how the person said he/she can get Google Voice number with FreedomPop VOIP number. I am guessing maybe that person was doing a port-in instead of phone verification???
My Google account was created during the Gmail beta period, and I was able to get Google Voice, but to get a different Google Voice number, I had to use my old T-Mobile prepaid for the verification. FreedomPop VOIP or anything that uses Bandwidth.com (freedompop, voip.ms) VoIP will not pass the verification.
If the phone number has been used by someone else in the past to verify Google Voice, then it will fail the verification.