In IP Office Manager, open the system's configuration.
Click User to display a list of existing users.
Double-click the user for whom callback is being set up.
Select the Voicemail tab.
In Voicemail Code, enter a pin code and confirm this in Confirm Voicemail Code.
Select the Source Numbers tab. Right-click and select add to add a new number.
Callback Number: Enter P followed by the destination telephone number. If you system requires an external dialing then that prefix must be included, for example P901923555456. If connecting to a cell phone or pager system that expects digits in separate sets, use , (comma) characters to add pauses to the telephone number dialing.
Trusted Source: If calls from the callback number include ICLID, you can set that number as a trusted source. In that case no request for the user's voicemail code is made following the callback. Enter V followed by the CLI displayed on calls from the callback number, for example V01923555456.
Click OK.
Click to send the configuration back to the IP Office.
If the only changes made were to user settings, select Merge Config.
to send the configuration back to the