functions.php

<?php
/**
 * Retrieve payment confirmation data.
 */
add_action( 'init', function() {
	$data = \SimplePay\Core\Payments\Payment_Confirmation\get_confirmation_data();

	if ( ! isset( $data['customer'] ) ) {
		return;
	}

	$payment = current( $data['paymentintents'] );
	$charge  = current( $payment->charges->data );
	$billing = $charge->billing_details;

	$name = $billing->name;

	// Do something with $name...
} );