You assume that everyone in the house saw the phone jump. Is that really what happened? Did anyone actually see it jump at all? Since no one was near the phone, perhaps they just heard it fall and assumed it jumped. Or maybe one person saw it move from the corner of their eye and the rest just heard it.
No, that's not what happened. Let me describe their living room. I'll try and do a diagram here:
__________________________________
stairs phone & table
______ open doorway __________
TV SET
LIVING ROOM
couch
________________________________________
They were sitting on the couch watching TV. They have a full view of where the telephone was. It didn't just fall off the table; it landed close to the bottom of the stairs, which is a good 5 feet from the table. The boys were sitting there with them watching TV, so it wasn't them playing a joke; in fact it apparently scared the hell out of them. The daughter was at her boyfriends house. They have no pets. No one else was in the house and as I've already observed: they have a full view of the telephone from where they were sitting on the couch and saw it fly off the table all by itself.
These are not fringe people. My girlfriend has a PhD and teaches Chemistry. Her husband works in Municipal Law and is (or was) himself a sceptic in the supernatural. However, the experiences they've had in this house has made him far more open to the idea that there's more to life than this one.
So rem, you tell me: from the view they had sitting on the couch, where they can clearly see the telephone and what happened: how did it move like that on its own?