We're so sorry to hear that you are having an issue making your purchase. On the checkout page, you should see fields for your name, email and below this, a country location box. To the right of this is a space to input your Postal/ ZIP code:
Sometimes this field can be auto-filled with your email address depending on your browser settings, so I would definitely double check if this is what has happened here! If you are still having trouble, you can always contact us and we'd be more than happy to help.