Snippets: Alter WooCommerce Order Received Title

function myprefix_title_order_received( $title ) {
    if ( function_exists( 'is_order_received_page' )
        && is_order_received_page()
    ) {
        $title = "YOUR CUSTOM TEXT";
    }
    return $title;
}
add_filter( 'wpex_title', 'myprefix_title_order_received', 99 );
All PHP snippets should be added via a child theme's functions.php file.