User numbers are those that can be assigned to individual people on their Skype for Business client and/or compatible VoIP phones. Service numbers are those that can be assigned to a call tree (auto-attendant or call queue), dial-in conference, and the like. To many, this seems like a minor distinction, but trust us, it isn't.
For reasons we find difficult to understand, these two types of number seem to be run by completely different departments within Microsoft. Maybe someday they will fix that. So far, that hasn't been the case. Perhaps this book will help call attention to the problem. Based on the volume of complaints in public forums and suggestions in user voice, Microsoft probably already knows. ...
