You have to have a registable service on a ATA, many people here prefer callwithus.com, you can register callwithus on your ATA, then let IPkall forward call to callwithus, GV can forward call to IPKALL.
the callin path is GV ->IPKALL ->callwithus ->ATA, with IPKALL you do not need GV.
callout: ATA -> callwithus
