I would say speak to the manger and explain why you need a refund. If you don't get anything done there then call your bank and explain the charges made on your card. So either way you can get your money back.
It depends on the reason you want the refund. If it's a valid reason, I would go to the manager face to face and tell him what it is. They are a business and of course want you to come back. The manager is also a person, explain it to him in a way that makes him understand where you are coming from... They will probably refund you the money or give you a credit for the next time you do want to go. Good luck.
I've found the best way to get a refund is to bribe them with money.
You dont.... Or you can just go ask them nicely for a refund.
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