You're home alone at night...
...you've put your phone down somewhere but you can't remember where that was. After looking around for some time without finding it, you decide to use the home mobile to ring it and find out where it is. You dial the number on the mobile and then hear your phone ringing in another room for a few seconds before abruptly stopping on the second ring. You put the home mobile to your ear and hear heavy breathing on the other end...
I came up with that scary story myself.