Stranger in a strange land

Our company has decided that if people overpay for an order (this actually happens quite regularly…to the tune of several thousand dollars per month), we won’t refund their money, but rather give them a credit towards a future purchase. We will only send a refund if they call in and complain. I don’t even know what to say. Can this be legal? The higher-ups are so nonchalant about it, it’s making me question whether I’m the crazy one. I’m baffled.