Amex Credit Card Complaint

Amex Credit card department,

Billing statement Maryland

American Express that I signed up for because it made it easier to shop at -, has repeatedly overcharged interest. I finally decided to cancel the card, called for the payoff, wrote a check for that amount and sent it that day. They cancelled the card but they are now charging $9.00 on no purchases and saying that I owe interest on previous charges.