Double payments when using card mashine in store

Hi <br> This has happened twice where my money gets taken of my card when I swipe in the store but the card mashine said unsuccessful. I would like to speak to someone regarding this matter but I just get passed around how can my transactions be Going through on my card but not the store. <br> Why have I not been refunded and why is it so difficult to fix this problem as I have heard many people complain about the same thing. <br>