Unfortunately this doesnt fix your problem, but we just implemented Ringcentral and I have the same gripe about the VVX250 phones. Especially the directory. The App works as its own directory, but not everyone has an assigned extension for us, so they cant use it.

For displaying the Ext number on the phones themselves, the only workaround I implemented was to have the Ext number right before their first name. So my name is Cody Sumner, but in ringcentral I am 2001 Cody Sumner. Just so my extension displays on the phone. I hope someone comes up with a better solution than that though.

Cody -

In a meeting today with a Ring engineer, they enabled the following option for me (see screenshot below. This will change the line to show the extension instead of the name. This is a hidden option by default for some stupid reason. An engineer will have to enable it on your account. It still doesn't help the address book, but at least I can have phones with the extension displaying now. Hope it helps.

This was exactly it for displaying the Ext. I really cant wrap my head around the feature being hidden though. Just for further details as the tech I spoke with didnt know what I was talking about at first. The feature that Joey screenshotted is within the phone settings, not the user settings.

Thanks for sharing this info, @Joey Martinez @2001 Cody Sumner
This will potentially help other folks who have run into this roadblock!

We went the other route - adding the extension to the end of the last name. This way, the icons (if staff didn't put in a photo) would have their correct initials, and in doing the Search, it came up - in my opinion - a little more readable.

So I would show up as:

Joe Cache - 1601

and the icon would show (JC) [now that they fixed the messanger issue - no longer showing as (J1) - gads...]

We also then had to edit the voicemail auto-annouce to take out the '-1601' so it wouldn't say it when someone got to voicemail.