Custom success message

Hi, I want to update the WPCF7 form success message.

I need to do it using PHP because I’m using that to generate a WooCommerce coupon on form submission. That’s all working. Now I need to update the form success message to include that generated coupon code.

Below is my 15th ( clumsy ) attempt.

add_filter('wpcf7_before_send_mail','dbo_update_form_message',10,1);

function dbo_update_form_message($messages){
	$messages = array(
		'mail_sent_ok' => array(
			'description'
				=> __( "Sender's message was sent successfully", 'contact-form-7' ),
			'default'
				=> __( "Thank you for your message. It has been sent.", 'contact-form-7' ),
		),
    );
    return $messages;

}

I’ve also tried
add_filter('wpcf7_mail_sent','dbo_update_form_message',10,1);
and
add_filter(wpcf7_messages,'dbo_update_form_message',10,1);

clearly I need help.

Thanks in advance