We use special telephone number ranges at the events.
|Range||Use / Reserved for|
|1000 - 1999||Orga / Event / Venue|
|2000 - 2099||Eventphone / PoC|
|2100 - 9899||public range|
|9900 - 9999||Internal, special services, services that offer added value for several users.|
Just because a number is not listed in the phone book does not mean that it is not used.
If, during the creation of a number in GURU, a message appears telling you that the extension is already in use, then this is correct. There is no reason to open a support ticket.