I figured it out - configuring from back end instead of Obitalk portal:
Service Providers -> ITSP Profile A -> General -> SignalingProtocol = SIP
Service Providers -> ITSP Profile A -> General -> Name = Simon
Service Providers -> ITSP Profile A -> SIP -> ProxyServer =
gvgw2.simonics.comService Providers -> ITSP Profile A -> SIP -> RegistrarServer =
gvgw2.simonics.comVoice Services -> SP1 Service -> AuthUserName = GVmynumber
Voice Services -> SP1 Service -> AuthPassword = MyPassword