You can delete a single mailbox by phone, but a you cannot delete a range of mailboxes by phone. You can only delete a mailbox from the administrator’s mailbox.
To delete a mailbox by phone:
Press D (the 3 button) to delete a mailbox.
When prompted, enter the mailbox number to delete. You hear the message "Mailbox [number] has [number] messages total. If you really intend to delete mailbox [number], enter the mailbox number again."
Enter the mailbox number again. The server responds with "Mailbox deleted," and returns you to the Administration Menu.
Press X (the 9 button) to exit from the Administration Menu.