In most Drupal sites I've ever worked on I've had to add text to the standard "contact" page, e.g. address, phone number or sometimes even instructions on how to use the form. To do this you have to use a custom block. There should be a text field for the contact form that a user with permissions to manage the form can edit whenever they like because (a) that person might not have permission to edit blocks and (b) blocks don't always sit in the right place on the form in every theme (e.g. the block text appears above the "Contact" page header or below the whole form, etc, when you actually need the text to appear between the page header and the form).