Living in London and not having a landline, I've been using
Skype to call people in Australia; recently, I have found its reliability to be somewhat variable. Sometimes when I call a mobile phone number, I get a recorded announcement saying that the phone in question is not connected; at other times, I get a nameless voice-mail message, which may or may not belong to the person I wanted to call.
Furthering the annoyance, Skype's charging mechanism is a bit unreliable, and sometimes it goes from Ringing to Call In Progress when the phone is still ringing; there goes another 16.5 Euro Cents.