I have a Nokia e71, and everytime I call someone the caller ID on the person's phone says "private caller". How can I change this?

Telephone settings
Select Menu > Tools > Settings > Phone.
Select from the following:
• Call — Define general call settings.

Call settings
To display your phone number to the person you are
calling, select Call > Send my caller ID > Yes. To let
the network determine whether your caller ID is sent,
select Set by network.

You would go into Menu, Phone settings or call settings, then choos Network, and select Caller ID settings, and there should be some options like show my id or block my id.