Unauthorized debit to my checking account
Collectcorp sent a notice to my adult son regarding an amount due $3499.78 for American Express Credit Card. I mailed a check to Collectcorp for the total amount due on my son's behalf. I called the representative to follow up and was advised that $288.98 was still due to pay the account in full. I provided my account number and authorized a debit for $288.98. A month later, without authorization or communication, Collectcorp made two debits to my account in the amounts of $81.86 and $2.99. I called and left a phone message for the representative, but he hasn't returned my call.
How should I proceed.