Let me tell you a sad story.
When my wife ran off with another man I was deeply upset.
So I rang her and left very personal messages on that awful BT 1571 service.
(for non-brits it's a free voice-mail service but you cannot leave an outgoing message unless you pay a monthly fee)
As it turned out, I was ringing the wrong number but even though the recipient knew me he did not bother to tell me. You're an arsehole Dave!
So, you takes your chance when dealing with these sorts of "services". Just don't go there.
P.S. I'm glad now that she left. :)