remove_action( 'woocommerce_single_product_summary', 'woocommerce_template_single_title', 5 );
    function woocommerce_add_custom_text_before_product_title(){

    $custom_text = 'My Custom Text';
    the_title( '
'.$custom_text, '
' );
}
add_action( 'woocommerce_single_product_summary', 'woocommerce_add_custom_text_before_product_title', 5);