Who Is He Speaking To?

One day the manager of a big office with
many employees in many different rooms
picked up his telephone and told his secretary
that he wanted to speak with his sub-manager.

    But there was something wrong with the
telephones and, instead of hearing the sub-manager's
voice, he heard another voice
saying:
      'I think the manager is an old fool, don't
you?
      Before there was any reply, the manager
shouted, very angrily, 'Do you know who
you are talking to? I am the manager!
        'Oh, are you?' said the voice. 'And do you
know who you are speaking to?'
         'No, I don't,' shouted the manager.
         'oh, good,' said the voice, 'then you won't
be able to sack me!'