Product: Debt collection

I had an account with American Express which they sent to a collection agency in order to collect from me. I paid the full amount and American Express recorded that I had satisfactorily paid the account off. This was about 2 years ago and earlier this year a collection agency called me, identified themselves as American Express Legal Department, and asked me to pay a sum of over {$4000.00} for the account which was closed 2 years prior. They stated I still owed American Express the full amount, they were extremely rude and refused to give any information in written form. They stated that I have all the information and they were not obliged to provide anything. 

I immediately called American Express and initiated an XXXX case Ref. XXXX. I provided them the information and phone number ( XXXX - the fraudulent call was from this number that answers as American Express Legal Department ) of the caller and the they acknowledged/confirmed that this was the collection agency they have a contract with to collect. The agent called the number and the person who answered said they could not locate my account information and refused to help us further. The AMEX agent who opened the case said they would refer this to their back office and that someone would follow up with me. I never received a call or any communication. 

Today, XX/XX/XXXX, I received a call from XXXX again and a guy advised me he is from American Express ' Legal Department and he needs to collect over {$3000.00} from an account ending in XXXX. I asked him to please send me information regarding this debt via e-mail, he replied that they have already provided me with the stipulated details in the past therefore he does not need to send me anything. I now asked if he was actually refusing to provide any information via email and after a long quiet pause he advised me that he needed my email address and other personal information so he can update his records. At this point I advised him that they had all my information and to please send me the details of such debt to the e-mail address that American Express has on file. He then stated he needed information, paused again and then hung up. 

I called American Express at XXXX to report the fraudulent activity and asked the representative to update my XXXX case. She updated the case with the above details, apologized that I was going through this and then advised me that she could not do anything to help me. I asked for a supervisor or someone in a legal department and after placing me on hold she came back and told me no one could help me as this is a closed account and they are not responsible for the Debt Collection Agency 's activities. 

At this point I advised them that if they can not protect me from the company they hired and given my personal information to then I'd have to report them to the FTC and seek legal counsel. She replied by advising me that she could no longer talk to me because I mentioned I may open a legal case against them. I believe that this collection agency is acting maliciously and fraudulently attempting to collect thousands of dollars from me, they are extremely rude and threatening and American Express is doing nothing to protect me.