Phones not displaying "On Another Call" message

[dangercrane]

I've got a BCM50 with a mix of 1140E's and T7316's. When a user called another user who was on a call, they would get an "on another call" message. Somewhere along the line, this option stopped working and I can't figure out how to turn it back on. Can anyone help!!!

 

[snowman50]

Go to Capabilites and tick DND
This will prevent the second call ringing the phone.
The reason you get this message is because the second call is ringing the phone telling the calling party they are on another call already.