Intentionally Double Charged For Item

I was intentinally double charged for one of the items i bought. The cashier and the packer were acting very strange at the time and it did not make sense to me. 2 days later, I came across my slip and for some reason decided to check it and it seems I was double charged. I say its intentional because i remember seeing the two ladies signaling to each other and I found that really strange. Now it makes perfect sense.