Thanks for the explanation. It does indeed sound like there’s no convenient solution till your whole system gets revamped. To briefly explain *why* I don’t want your voicemail enabled: I use my USMobile number as a forwarding line for Google Voice. Google Voice’s voicemail is frankly superior to yours so I want to use it exclusively. When your voicemail kicks in it interferes with Google Voice’s operation, causing me frustration and a real mess. I’ll give some thought to whether I want to be bothered with going through a quarterly exercise of calling and re-disabling your voicemail.
Configuration guides of tested IP phones, soft phones, door phones, audio alerter devices, and intercom devices.

Maintenance gives you access to upgrade PBX firmware, check logs and troubleshooting.
After setting the number on your voicemail, you must also record a personal voicemail greeting. Follow the steps below. Start the Phone app. if you don’t see the numeric keypad, tap “Keypad” at the bottom of the screen. Tap and hold the “1” for about two seconds until the phone automatically calls voicemail. Immediately tap “3” to access voicemail settings. Listen to the options. On most voicemail systems, tap “2” to start the process to record a new greeting. The current personal greeting will play; then tap “2” again to record a new greeting. Say the greeting you want, and tap “#” when you’re done. To save the greeting, tap “1.” The personal voicemail greeting has been set. Hangup the phone. How to setup voicemail using a Visual Voicemail Applications