If the bank or credit card company wouldn’t reverse the charges when you reported your card lost or stolen, you can use the sample letters below to dispute the charges:
Dispute letter for credit card charges: https://www.identitytheft.gov/Sample-Letters/dispute-credit-card-charges
Dispute letter for ATM or debit card transactions: https://www.identitytheft.gov/Sample-Letters/dispute-debit-card-transactions
Dispute letter for if someone misused one of your existing accounts: https://www.identitytheft.gov/Sample-Letters/identity-theft-dispute-charges-existing-account