Product: Credit card or prepaid card

On Monday XX/XX/XXXX I received my monthly master card statement from Bank of America. I opened it to find a Balance transfer check ( check # XXXX ) charge in the amount of {$4800.00} plus fees of {$190.00} with a Transaction date of XX/XX/XXXX and a posting Date of XX/XX/XXXX and interest of {$6.00} for a total owed of {$5000.00} I havent used this account in a while and had a XXXX  balance prior to this statement. I called Bank of America to dispute this charge. I also had my son XXXX  talk to the rep as I am XXXX of XXXX. The rep canceled my card and said they would issue a new one, which they did. We told the rep I never made this charge or used a Balance transfer check and didnt have any balance transfer checks. He asked if I recently consolidated my debt, we told him no, and that I didnt have any debt to consolidate. All of my bills were paid. He said they would issue a temporary credit on my account while they investigated this and the investigation could take 7-10 days. 
On Tuesday XX/XX/XXXX I received 2 separate letters from Bank of America 1 Dated XX/XX/XXXX stating a Temporary credit of {$4800.00} was issued while they conduct their research. The 2nd letter also dated XX/XX/XXXX stating they had completed their review and that they confirm the charge either covered an overdraft on credit card or was a balance transfer that went directly into an account in my name. This letter also contained a dispute form to fill out and send back which I did the next day XX/XX/XXXX. I also called the number on this letter and again with my son and stated I did not make this charge or use a balance transfer check. I had no debt to consolidate and I didnt receive this money in any account of mine. The rep asked if I did a debt consolidation with XXXX XXXX. We again told the rep, No I didnt and that I had no debt to consolidate and have never heard of XXXX XXXX. We gave the rep the Police department incident ID number as its an ongoing investigation they didnt have a full report. The rep said they would look into this again and also issue temporary credit. 
On Monday XX/XX/XXXX I again received 2 separate letters from Bank of America. 1 Dated XX/XX/XXXX Stating they were again looking into my claim and I needed to fill out and complete the enclosed fraud statement and return it within 10 days of receiving it or they would not be able to complete their research and have to deny my claim. I completed that form and mailed it using next day service from US postal service. The 2nd letter dated 2 days after the 1st letter XX/XX/XXXX stated they completed their re-evaluation of my credit card dispute and their decision to decline my fraud claim had not changed ( So they completed their re-evaluation in 2 days without that fraud statement that they requested within 10 days ) and that their research confirmed while you personally didnt make the charge ( s ). We confirmed it was made by an authorized user on the account or someone who has permission to use the card. There was a number on the letter that said if I had any questions to call, I called that number with my son XXXX When we told the rep we were glad they admitted I personally didnt make the charge. We also informed the rep that there wasnt any other authorized user on the account or anyone else that had permission to use the account. The rep stated she showed that there was a XXXX XXXX  as an authorized user on the account and asked who that was. We informed her that was my other son who died in XX/XX/XXXX and asked her if they are trying to say he came back from the dead and made this charge. She said was sorry, but the account still had him listed as an authorized user. And that there wasnt anyone else authorized. Then she asked if I had an account with XXXX XXXX, I said I did not and again told the rep I had no debt to consolidate, all my bills were paid. I never received this money in any account of mine nor did I receive any benefit from this money in anyway. I told her by Bank of Americas own admission on the denial letter that I didnt personally  make this charge and the only other authorized user on the account died XX/XX/XXXX, that this was obviously fraud. She said they would look into it again. 
On Tuesday XX/XX/XXXX I received 1 letter from Bank of America dated XX/XX/XXXX again stating they were denying my claim of fraud and again confirmed while you personally didnt make the charge ( s ). We confirmed it was made by an authorized user on the account or someone who has permission to use the card. 
The Police investigator thats looking into this said Bank of America told him that a Balance transfer was attempted back in XX/XX/XXXX for {$18000.00} but was stopped by Bank of America and deemed to be fraud. 
The Police investigator has gotten a subpoena for XXXX XXXX to determine who got this money, but said it could take a while, in the meantime Bank of America has removed the temporary credits and insists that this is a charge Im responsible for and need to pay off. 
So Bank of America admits fraud was attempted a few months prior, they have stated I personally didnt make this charge and the only other authorized person on the account died over 7 years ago. But yet they still insist this is not fraud and I need to pay them. 
I want to reiterate. I did not make this charge/ balance transfer, I did not authorize anyone to make this fraudulent charge/ balance transfer. I did not receive the money from this fraudulent charge/ balance transfer. I did not receive any benefit from this fraudulent charge/ balance transfer.