How to show phone number only to certain customers or only for Priority 1 requests?

[Robert Werner]

I'm still in the early stages of setting up my company's JSD customer portal and KB.  Our goal is to encourage users to:

1. First use the KB to try to find a solution.
2. Failing this, to then submit a request.
3. Failing this, or choosing not to use #2, to call us - but only for Priority 1 issues.

I'm curious how other JSD Admins have set up their customers portals so that the support phone number is restricted in some way?  Or, is doing so, generally bad practice?

Robert