Dollar Tree review: item incorrectly scanned twice and clerk refused to issue money back

I paid for the items I had purchased and when I checked the receipt, I noticed that the Clerk scanned one item twice which brought the total amount to six when I only had five. I was still standing there and hadn't even picked up my bags yet. I checked in the bag containing the items and it was only five. When I brought it to the attention of the Clerk she told me Dollar Tree doesn't give refunds and I would have to do an exchange. I asked her what I would be exchanging when the item doesn't exist. She insisted it was the store's policy to only exchange and not issue refunds. Again, I explained that she scanned one too many items which wasn't my fault and that I wanted my money. I asked to speak to the manager and she told me she was the manager. I don't understand why customers can't get their money back when clerks over-scan. The customer pays for an item that doesn't exist and then is told that they can "exchange" the non-existent item. This is ridiculous and should not be allowed to happen. I filed a complaint on Dollar Tree's website that same evening but never heard back about giving me my money back. I tried calling customer service and was either left on hold until the call dropped off or when someone answered was told I had the wrong department and was given the "correct" number to call which happened to be the SAME number I just called.