Alien phone calls, static? Voices? Demons?

Just came across videos on YouTube with people saying how their cell phones are getting wierd noises, before, during and after phone calls. I wonder if anyone here has heard of this?

[link to www.youtube.com]
[link to www.youtube.com]
[link to www.youtube.com]
[link to www.youtube.com]

I thought it sounded like chirping or voices talking really fast and so I tried to slow it down in programs like Audacity and at around 1/4 of the speed, you can barely make out voices... but there is so much distortion or something it's very hard to make much out.

What I have decoded so far are phrases like "we'll have a really good time", "I am hungry" and other.. not so good phrases

Was this a hoax that was popular for a while?
Aliens attempting to communicate?
Demons?
Wondering what your thoughts are...

The parts that get me, are the "bad" phrases, and the responses. I can't find it again, but there was one where a guy says "Helloooooo" and the voices, in a whisper, say "Hi", and then the fast static/garbled/talking starts again. And at the end, the guy says "Hellohellohello" and the voices seem to get pissed at him and give a long "heeeeeeeellllllooooooooo", which cuts out off/on during the phrase, as if it is upset and mocking him not hearing them....