Why wasting money on buying the method? there's no method. simply sign up google voice account with US Proxy or VPN. and you will get one number per google account for free. then, you need to verify that number. to do that, you can use android applications which offer US numbers such as SecondLine or Textnow, or use sms-verification services. and that's all.
your google voice number will be verified.
simple.
looks you have never used google voice. they dont accept voip numbers to verify kid