I don't know if this is a bug in the Android, a malfunction of the device, or this is something normal, because I wasn't able to find anywhere else something related to this thing. I am really...curious if this happens to anybody else, and if it does, this means that it is possible for those ones with Nexus One devices and Android 2.2 to speak for free, but for a limited time, because the call stops after 10-20 seconds (depending the carrier).
So, does this thing happen to you too?
p.s.: If you need to update to Android 2.2, here's how to do it.