I'm not sure what you can do since it was paid by debit, but I know that with credit cards, you can call the credit card company and have them do a chargeback. Maybe contact your bank and see if they can do something similar? But first I would go back to the restaurant and speak to the manager. Show them your statement and explained what happened. Either they will refund you right away, or they'll have someone look into it. If they choose not to do anything about it, then definately see if you can do some type of chargeback. Good luck