Amex Credit Card Complaint

Amex Credit card department,

Closing/Cancelling account Texas

when my renewal for my membership fee from american express was up, i called and cancelled my card. i have a letter from them acknowledging my cancellation .they continually charge my card that membership fee and charge me late fees.they know say i owe them about - dollars all from a membership fee and late charges. i told them i dispute the charges and told them to send it to a collection agency so i can bring it to arbitration .they do nothing but continual to charge me late fees