Gmail phone verification - Nexmo, Plivo don't work?

I intented to phone verify bunch of Gmail accounts on my own, and purchased few US phone numbers with Nexmo credits. Their support told me that they don't allow Gmail verifications and they can ban me because of that. WTF!? I bet that with Plivo is the same.

Can someone suggest me some service where I can purchase US phone numbers for Gmail SMS verification?

Google Voice is the way to go.

I talked today with Plivo representative, they allow Gmail verifications.