My brother just called me at work because I did it to him this morning again. He said somebody has been calling him saying it's the police, have your bags packed, etc... He asked if it was me. I busted out laughing. I couldn't hold it back.
A friend of mine called me and told him to call him when I go home for lunch. He didn't say what it was about. I gotta really work on holding it back. I woke his ass up at 2:30am and said the police would be there at 3AM. He goes to work at 5am. He probably never slept after that call.
No you don't get charged. It's just a demo thing. If you noticed, at the end of the message it does rap off your IP address. To the average person, they won't know what those numbers mean. Just don't ever make any threatening calls obviously.