add_action( "propertyhive_property_imported_acquaint_xml", 'acquaint_username_to_office', 10, 2 );
function acquaint_username_to_office($post_id, $property)
{
    switch ( (string)$property->username )
    {
        case "Sally Smith":
        case "Gordon Greg":
        case "Tim Tommy":
        {
            update_post_meta( $post_id, '_office_id', 123 ); // replace 123 for the relevant office ID
            break;
        }
        case "Henry Harlem":
        case "Phil Potter":
        {
            update_post_meta( $post_id, '_office_id', 321 ); // replace 321 for the relevant office ID
            break;
        }
    }
}