The above error may be produced when attempting to synchronise users. It will be most frequently be associated with the additional information: 'because it is restricted for the user service plan: MCOEV_VIRTUALUSER,MCOProfessional'
What Can I Do?
The reason for this is that the user has been given the Virtual Phone System Licence rather than the regular Phone System Licence. All you need to do is amend the Phone System Licence and the error will clear on the next Sync.
The Virtual Phone System licence should be reserved for Service Accounts.