I have a PBX (NEC sv8100) connected to a FIOS Land Line service(Frontier). I get phantom calls at all hours and can't stop them. Usually calls will occur on both landline numbers at the same time. The ring tone will ring twice and then degenerate into continuous static. The system voicemail will answer but a blank message is left. The caller id says "Outside Caller", but no number. Return call service (*76) and call logs show no call. Blocking services (NoMoRoBo.com) and unidentified caller block (*77) don't work. I'm at my wits end. Can anyone suggest how to get rid of these annoyances? Thanks for any help