If your credit or debit card was lost or stolen, immediately contact your bank or the credit card company and report the cards lost or stolen. They should be able to tell you the last few times the card was used. If you don’t recognize any of the recent transactions, ask your bank to reverse those charges so you don’t have to pay them. If they won’t reverse the charges, see Step 3.
If someone stole your checks, contact your bank first, and also one of the major check verification companies to report the theft and to stop payment on the stolen checks: