Custom shortcode not being included in content paragraph [duplicate]

The ‘contact’ function should return a string instead of echoing.

So the above, should look like:

function contact() {
  $contact = get_field('contact',options);
  return $contact;
}
add_shortcode('contact', 'contact');

Shortcodes are written by providing a handler function. Shortcode handlers are broadly similar to WordPress filters: they accept parameters (attributes) and return a result (the shortcode output).

See the codex for Shortcodes