add_customer_detail_on_email_woo.php

// class-wc-emails.php:443

public function customer_details( $order, $sent_to_admin = false, $plain_text = false ) {
		// if ( ! is_a( $order, 'WC_Order' ) ) {
		// 	return;
		// }

		$fields = array();

		if ( $order->customer_note ) {
			$fields['customer_note'] = array(
				'label' => __( 'Note', 'woocommerce' ),
				'value' => wptexturize( $order->customer_note )
			);
		}

		if ( $order->billing_email ) {
			$fields['billing_email'] = array(
				'label' => __( 'Email', 'woocommerce' ),
				'value' => wptexturize( $order->billing_email )
			);
	    }

	    if ( $order->billing_phone ) {
			$fields['billing_phone'] = array(
				'label' => __( 'Tel', 'woocommerce' ),
				'value' => wptexturize( $order->billing_phone )
			);
	    }

		$fields = array_filter( apply_filters( 'woocommerce_email_customer_details_fields', $fields, $sent_to_admin, $order ), array( $this, 'customer_detail_field_is_valid' ) );

		if ( ! empty( $fields ) ) {
			if ( $plain_text ) {
				wc_get_template( 'emails/plain/email-customer-details.php', array( 'fields' => $fields ) );
			} else {
				wc_get_template( 'emails/email-customer-details.php', array( 'fields' => $fields ) );
			}
		}
	}