Double charge on bank card.

My wife bought a whole lot of stuff from them, when she swiped her card to pay they said it didn't go through and she must swipe again. A double amount was debited from her account. They said that they would sort it out if it wasn't reversed. The next day when my wife queried it they claim that there is no problem and they tal**** up fine so they will not be retuning the money. They got very rude and aggressive with my wife and refuse to do anything about it. Even though she has proof on her bank statement that they double chatged her.