src/Checkout/Checkout.php
public function setContactDetails($email, $firstname, $surname)
    {
        $this->order->Email = $email;
        $this->order->FirstName = $firstname;
        $this->order->Surname = $surname;
        $this->order->write();
    }
public function setContactDetails($email, $firstname, $surname)
    {
        $this->order->Email = $email;
        $this->order->FirstName = $firstname;
        $this->order->Surname = $surname;
        $this->order->write();
    }
contact information