- To Setup -

step 1: go to Dial Settings / Inbound and select the number you want to use.
Step 2: edit the number, go to Default action tab and select External Voicemail.
Step 3: click OK and Apply Changes.
Step 4: go to Phones / Extensions and edit the extension you want to use.
Step 5: go to the 'User' tab and ensure 'Allow Dialout' is enabled. Check your voicemail password.
Step 6: click OK and Apply Changes.

- To test -

Call the inbound number you have selected.
Enter your extension and voicemail password, such as 100 and 1234.
Choose option 34
Enter the number you would like to call

- To automate -

You may find Johns' mobile number in your phone: 0612345678
You can edit your contact and change it into: 0201234567p100#p1234#p34p0612345678

If you now call your contact 'Mark Mobile' it will automatically dialin to the PBX, authenticate, and make the call.