If you see unfamiliar charges on your account, send a copy of your identity theft report to each of the three agencies listed in Step 2 and tell them which transactions on your report aren’t yours.
This sample can help you write a letter: https://www.identitytheft.gov/Sample-Letters/identity-theft-credit-bureau
If they continue trying to collect from you, call the FTC for further help.
If you are being hounded by a debt collector for a transaction that wasn’t yours, send them a letter with a copy of your information and ID theft report. Use this sample to help you: https://www.identitytheft.gov/Sample-Letters/identity-theft-debt-collector