There are two ways to set up access so that users can dial in from an off-net telephone and manage their voicemail.  One is by pointing a DID directly to the voicemail system, and the other is by creating an access code in an auto attendant.  Either of these methods will prompt the caller to enter their extension number and their voicemail password, and they will have complete control over managing their voicemail, the same way they do as when they dial 98 from their extension.

If you already have an unused DID on your phone service account, log into the PBX as an administrator and point that DID to the voicemail system.  DID Management->Point DIDs.  Instead of picking a target from one of the drop-down menus, check the box near the bottom of the screen for Remote Voicemail.  If you don't have an unused DID and you get your SIP service from nexMatrix, we can obtain a new number for a nominal cost.

The alternative to a dedicated direct dial phone number is to create access through an auto attendant.  We recommend assigning a two-digit keypress code for this function, to avoid having customers route their call to your voicemail system accidentally.  Enter your desired code in the digit field, and select Check Voicemail for Extension from the drop-down menu.  Click on "Add Route", then on "Save Changes to Attendant" at the top of the screen.   After reloading the PBX, your users will be able to enter the access code during the Attendant announcement playback and reach the system prompt to enter their extension number and password.