The assistant of the Chinese Supermarket

Dear, Sir/Madam,
      I´m Big Foot one of the customers of your Chinese supermarket. I had a problem with your assistant of there. I had bought a pair of green boxing gloves. But, when I return to my house I looked the receipt and the cashier charged them twice. So, I went again to the supermarket and told to the cashier what has happened but he didn't believe me. I'm sorry of it sounds aggressive but, it was a lack of respect.I ‘m trying to ask you if you can talk to him to give me my money back, talk with him because he doesn’t want to give me, because he said that I was lying. Also, I showed him the receipt but he continued distrusting me. Well, if there is a positive or negative answer tell me as soon as posible.                                                                                                                                      Thanks Big Foot