Restaurants using Survey Studio have the facility to send receipts by email. If you receive an e-receipt that you do not recall requesting, presumably the diner misspelt their own email address when they asked for their e-receipt, so you received it in error.
If you've received a receipt that is not for you please forward the email with the receipt to Survey Studio support. We will remove your email address from our system and you will receive no further communication from us or the restaurant.