Tessa and The Phone Ritual

Over the last several months, Tessa has gotten into a habit.  It's very weird and we speculate as to why she does it.  As soon as I get on the phone with anyone, she quietly gets up and disappears to the basement.  I'll go down there and find her curled up in the darkness.  I don't know whether my talking on the phone disturbs her sleep so she moves, or I speak more loudly on the phone and she thinks I'm upset with her.  But as soon as I hang up the phone, I hear her collar jingle as she comes bounding upstairs again.  Such a weird furry friend.