Disable entering extension when the call has gone to a voicemail message.

If an external call dials a direct line on your numbers list, it shouldn't have the ability to transfer to any extension on your extensions list. I had an external number dial a direct line that goes straight to voicemail, but they were able to hit certain keys on their numpad that redirected them to a call queue that has no relation to the direct line they dialed. That should not be possible in my opinion.