Amex Credit Card Complaint

Amex Credit card department,

Payoff process Louisiana

I owed a large amount to American Express Consumer credit card. I refinanced my home and was able to roll the debt into my mortgage. I received a check for the payoff from my mortgage holder ( - - ), contacted American Express collections service in -, AZ for the full payoff on - -, 2015. The payoff amount provided by the collection service was - plus $270.00 in interest accumulated. I Mailed via - Priority Overnight, Saturday Delivery the requested funds to the debt collection center in -, AZ. so the payment was received on - -, 2015, in full. American Express Failed to post the payment until - -, 2015. They then proceeded to Charge me interest on the outstanding balance, after receipt of my payoff in full. Since then, they have charged interest on the interest and late fees, yet I was not contacted by their collection agency regarding any difference in the payoff amount and the amount submitted. Today, they have reported the account as delinquent and posted a negative notation on my credit report, and when I contacted them to inquire about what had occurred, a person at a call center in -, told me that the payoff amount provided by the company was basically worthless, since interest accrued from that day till the payment posted. What legal recourse do I have.