I noticed that when I'm on a call with someone and another call comes in, I am unable to link the two. If I'm talking to someone there is an "add a call" button present. Hitting this button links the the two calls. However, this button is replaced by a "swap" button when I'm talking to someone and another call comes in and I pick it up. Does anyone know how to join in this situation? I'm sure I'm just missing something simple. Thanks.