If you see a charge on your credit card from Amazon Prime, the first question I have is did you order something from them? If you did, have you received it? If you didn't, there are a couple of things to do. First I would call Amazon Prime, here is the customer service contact page off their website.
call them and make sure the item on your credit card statement was not ordered by you or someone in your family, Christmas is around the corner. There should be a reference number on your statement to track the purchase transaction. Talk to them. If you didn't do the transaction they should know, they will be able to see if this seller is putting through a lot of fraudulent credit card purchases and if so shut them down. The next thing you will then have to do is call your credit card company and tell them your card information has been compromised. Check to ensure no other fraudulent transactions have been completed. The credit card company will have to cancel your card and send you a replacement, which will probably take 2 weeks to receive. The 1 800 number for the credit card customer service will be on the back of the card.