Email customer immediately upon first failed payment

wcs_my_custom_retry_rules.php

<?php

function wcs_my_custom_retry_rules( $default_retry_rules_array ) {
	return array(
		array(
			'retry_after_interval' => DAY_IN_SECONDS / 2, // how long to wait before retrying
			'email_template_customer' => 'WCS_Email_Customer_Payment_Retry', // email customer immediately upon first failed payment
			'email_template_admin' => 'WCS_Email_Payment_Retry',
			'status_to_apply_to_order' => 'pending',
			'status_to_apply_to_subscription' => 'on-hold',
		),
		array(
			'retry_after_interval' => DAY_IN_SECONDS / 2,
			'email_template_customer' => 'WCS_Email_Customer_Payment_Retry',
			'email_template_admin' => 'WCS_Email_Payment_Retry',
			'status_to_apply_to_order' => 'pending',
			'status_to_apply_to_subscription' => 'on-hold',
		),
		array(
			'retry_after_interval' => DAY_IN_SECONDS,
			'email_template_customer' => 'WCS_Email_Customer_Payment_Retry',
			'email_template_admin' => 'WCS_Email_Payment_Retry',
			'status_to_apply_to_order' => 'pending',
			'status_to_apply_to_subscription' => 'on-hold',
		),
		array(
			'retry_after_interval' => DAY_IN_SECONDS * 2,
			'email_template_customer' => 'WCS_Email_Customer_Payment_Retry',
			'email_template_admin' => 'WCS_Email_Payment_Retry',
			'status_to_apply_to_order' => 'pending',
			'status_to_apply_to_subscription' => 'on-hold',
		),
		array(
			'retry_after_interval' => DAY_IN_SECONDS * 3,
			'email_template_customer' => 'WCS_Email_Customer_Payment_Retry',
			'email_template_admin' => 'WCS_Email_Payment_Retry',
			'status_to_apply_to_order' => 'pending',
			'status_to_apply_to_subscription' => 'on-hold',
		),
	);
}
add_filter( 'wcs_default_retry_rules', 'wcs_my_custom_retry_rules' );