Issue description: The call is disconnected from VoIP side and it takes up to 30 seconds before the call is disconnected in GSM side. This typically happens if a voice mail is reached. If you make a test call to your cell phone, you can hear a busy tone.
This behavior can be caused by PBX settings or by 2N® VoiceBlue Next settings.
Please check following page:
Generate busy tone to GSM/UMTS is used to simulate an analogue line where you get a busy tone after disconnection. If you want the immediate disconnection, set this parameter to Disabled.
Similar settings could be necessary on PBX side.
More product information: