Re: “the cellular number you have called is not assigned” issue. The message means that number is not active.
What does it mean when a number is unassigned?
Unassigned numbers are phone numbers that are valid for your organization but are not assigned to a user or a phone. ... The unassigned number table can include both assigned and unassigned numbers, but it is invoked only when a caller dials a number that is not currently assigned.
What is an unallocated phone number?
The more technical reason why you get the “the number you have dialed is unallocated” call intercept message is that the number you are calling hasn't been assigned to a provider by the number administrator, or the number hasn't been assigned to an end-user by the provider.