Name Server Resource Record
Only the IP address of the nameserver may be changed. If the IP address is already in use by another record, it will fail. You will be notified by email about this. In this case, you may just use the nameserver which has been already assigned the intended IP address.
To change the name, please create a new name server record. If the name or the IP number of this name server record is already in use by another NS, it will also fail; you will get an error message by mail.