What category of lawyers do I need to sue walmart?

I bought lottery tickets at walmart on 5/15/2018. On Sunday, 5/20/2018 I went to check my tickets and discovered that they had given me my old tickets back and not the new ones. I went to the store and they watched video of the transaction which they did not let me see. The main person came out and said they could see me make the purchase and see the cashier lay down the tickets on the counter and see her ring them up. At that time the other manager said she saw me pick them up and put them back in my plastic slip I keep them in. The main person said all they could do was give me a copy of the receipt and I could call Lottery headquarters about it. She went to get the receipt and when she came back I said, " now, you saw me put the tickets back in my slip?" She said No, but the other lady said yes. On the way home I figured out what had happened. I had won money on the old tickets, but instead of stapling the old ones to the winning printout, she did that with the new ones.