I came across a similar situation in Family Dollar, where I noticed a discrepancy between the prices in the receipt and on the shelves of the store. The key to solving such issues is to remain calm and politely address the store staff. In my experience, most stores, including Family Dollar, have a policy of complying with displayed prices or offering refunds if they made a mistake. But once I ran into the resistance of the cashier and then decided to scare her that I would write
Family Dollar complaints as a last resort to find a solution. This worked because companies usually take customer feedback seriously.