Amex Credit Card Complaint

Amex Credit card department,

Identity theft / Fraud / Embezzlement Virginia

I received a debt collector letter states I own them money from - mastercard. However, I never apply and use this credit card before. I called debt collector, - - and - - and they do n't have any detail since they bought this debt. I called - mastercard and they said they do n't have any detail either since they sold the debt.