I have a freepbx 15 installation and 1 grandstream voip phone. The inbound route will direct call to grandstream phone if no one answered. The problem is: when someone call in and get into voicemail.
If he/she hand up immediately after voicemail prompt, it will leave a voicemail recorded busy tone and some garbage for 5 minutes. How can I configure voicemail not to record if phone hang up?