I'm running macOS Mojave latest iteration, I have the latest version of Skype for Business. Remove the user's Skype for Business Online credentials from the Windows Credential Manager. If you have Lync Server 2013, see the Skype for Business on Mac column in Client comparison tables for Lync Server 2013. Searching the interweb doesn't result in any positive actions I can take so I'm at a loss. With Skype for Mac, it’s possible to call anyone else on Skype for free regardless of where they’re located.
Users on Skype for Business Server 2015 cannot modify their contacts list in Skype for Business if a user account is enabled by the Skype for Business administrator for the Unified Contact Store (UCS) for Exchange. Same user account needs to be signed into Outlook and Skype for Business. I have this exact issue, but I can't find anything about it anywhere.
