I usually dial a number and then put the phone in my pocket (using a headset).
That doesn't work very well when the destination is busy since I never get a busy tone. I just get a "number is busy" message or something like that in the display for a couple of seconds.
Is it possible to get a busy tone instead?
This sounds like it may be something your carrier is doing when the number your calling is busy. If I call a number that is busy, I get a busy tone.