This is because you have not recorded your own personal voicemail message on that VoIP extension number which you have diverted to another line.  


Even though the line is on divert to another VoIP line - the mailbox for the line diverted still uses the voicemail message on that line if the call is unanswered. 


To resolve this you just need to record your personal voicemail message on your VoIP extension line - please follow the step by step instructions below: 


1. Dial +44 (0)1793 251125 or *98 from the handset that the line is set up on


2. Enter your mailbox number - this will be your VoIP line extension number - as shown below in red (this is a 6 digit number).



3. Enter your password - please see below where to find this: 



4. Dial '0' for mailbox options


5. Follow the voice prompts to record both an 'unavailable' message and a 'busy' message