Product: Credit card or prepaid card

I became aware of this " joint '' account, with SYNCB/JCPENNY, when my XXXX  score took a hit in the fall of last year ( XXXX ). I checked my score with XXXX and found out it was due to a " joint '' account opened by an ex-spouse on XX/XX/XXXX. Payments had quit being made and they closed the account around XXXX of XXXX and made it a charge off I believe during the fall of XXXX. ( Not sure of exact dates, unable to locate in my XXXX XXXX XXXX report ) I contacted my ex and asked about the card. She explained that she had money problems and had to file bankruptcy. I told her that by having my name on the account that her not paying her debts had hit my XXXX  score. She replied that it hadn't hurt hers. 
I filed a dispute with XXXX and XXXX. I checked back later and found that Synchrony Bank had verified the account as being mine. 
I then had numerous conversations with the bank, they still say it's my account. 
On XX/XX/XXXX I sent the bank a certified/signature confirmation letter and received the confirmation showing they received the letter XX/XX/XXXX. 
In the letter I explained that I have been divorced from my ex since XXXX and had not lived at or received any mail at her address since then. I also provided them with my current address and explained that this has been my address since XXXX. 
I also stated that, per the Fair Credit Reporting Act, I was requesting copies of any and all documentation that they had used to verify the information they had sent to the credit reporting agencies. I also requested copies of any and all applications or documents showing that I had applied for and signed to open this account. I also advised that it was my understanding that they had 30 days to comply with my request or to have this item removed from my credit report. 
The bank sent me a letter, ( dated XX/XX/XXXX ) addressed to my ex and myself, ( now that they had MY address ), stating that they were opening a fraud investigation. I called them on XX/XX/XXXX about their investigation and was told I would be receiving fraud investigation forms and that I had to fill them out and get them sent back by XX/XX/XXXX, or the investigation would be dropped. 
I then received another letter from the bank dated XX/XX/XXXX. It stated that the claim review was complete and they found that the payments had been made by me, the account had been opened more than 12 months with statements sent to me and that I had authorized, participated in or benefited from the purchase. 
I immediately called the phone number they provided in their letter. I again explained that I had never made a payment, received a bill or benefited from their credit card. I again advised that the " joint '' account with my ex was opened 23 years after our divorce, and I hadn't received any mail at her address since XXXX. I was advised they would reopen the investigation. 
I called the bank again on XX/XX/XXXX and asked if they had acted on my Fair Credit Reporting Act request dated XX/XX/XXXX, received by them XX/XX/XXXX. She advised that they had 60 days to act on it, and that I would be hearing from them. 
On XX/XX/XXXX I called the bank again and asked where they were with my request per the FCRA, and he said he couldn't find it. So I provided him with the date and the name of the person that had signed for it. He looked some more and sad he couldn't find it. So I said that I paid close to {$8.00} to send a letter to them and it was lost. He said that it wasn't lost, he just couldn't find it. I asked if he could explain the difference and he didn't respond. 
He then told me that he would be sending me an affidavit to be filled out and signed by me to start a fraud investigation. I explained that an investigation was ongoing and I really didn't care about their investigation, I wanted some action on my FCRA request. He again stated that he couldn't find it and would be sending the forms. 
On XX/XX/XXXX I received the forms and they were the exact same forms that I filled out and returned to them in XXXX. 
I called the bank on XX/XX/XXXX and after more than 2 hours and speaking with or being disconnected from at least 6 different people, no one could help. 
The charge off amount was {$3600.00} per one of their letters.