This happens to me when I get sent to someone's voice mail, they see I called, then call me back quite a bit.
The call in comes up as a second call, and I answer it. But I'm still connected to the outbound call that is now in the person's voice mail.
The interface to switch between these is really slick and easy to understand. But the only hang-up option is to hang up all calls.
How do I hang up on just one of the calls while leaving the other active? It's not intuitive (or maybe not possible) from the phone's screen.
This is on Sprint.