Yes, on the last call. But why would the impostors wait so long and thus increase the risk of exposure? And correct me if I'm wrong, but the context in which Kostikov's name eventually came up was rather innocuous if I remember correctly. The whole impersonation affair appears rather amateurish and impromptu in my opinion, not like a well concocted plan. And About Ruth Paine: I agree she's a suspicious character, but when Oswald was in Mexico he was also still on the FBI's watch list.