Product: Credit card

XX/XX/XXXX, I requested a balance transfer from my New Chase Freedom Flex credit card to pay off a {$500.00} balance on my XXXX XXXX credit card. On XX/XX/XXXX, I called Chase Bank because the payment had not posted to my XXXX account. On XX/XX/XXXX I was told by a Chase customer service rep ( XXXX XXXX that she would open a ticket to get the payment resolved and that it might take a few weeks. 
On XX/XX/XXXX, I called Chase bank again because the payment had not posted. A customer service supervisor ( XXXX XXXX told me that more time was needed to verify that " the check '' was cashed. 
On XX/XX/XXXX, I called Chase Bank again and spoke with a supervisor ( XXXX  ) who told me the following : The balance transfer was sent on XX/XX/XXXX by a 3rd party bill pay and that the 3rd party bill pay reached out to XXXX XXXX XXXX on XX/XX/XXXX ( who now handles the XXXX stores credit cards ) regarding the dispute about the payment on the account but but nothing was resolved. The XXXX also told me that on XX/XX/XXXX Chase requested the funds back from XXXX XXXX. On XX/XX/XXXX Chase was told by XXXX XXXX that they needed more time to track down the payment. On XX/XX/XXXX XXXX XXXX told Chase that they needed more time. On XX/XX/XXXX, Chase was told by XXXX XXXX that more time was needed. On XX/XX/XXXX Chase requested a stop payment and on XX/XX/XXXX was told again that more time was needed but there was no response from XXXX XXXX. Supervisor, XXXX then told me that on XX/XX/XXXX a letter was sent to me from Chase stating that they can no longer dispute the claim because XXXX  XXXX won't respond to them and that I needed to work directly with XXXX  XXXX to resolve my issue with the balance transfer. I never received a letter from Chase and the {$500.00} payment is still on my Chase Freedom Flex credit card. 
Anytime I talk to customer service at XXXX XXXX, I am told that more time is needed to locate the payment. On XX/XX/XXXX, I spoke with a XXXX  XXXX Senior Supervisor ( XXXX ) who told me that they needed hard copy document from Chase to verify that the payment was received by XXXX  XXXX. XXXX gave me a Case Investigation # and fax # where Chase could send the documentation. She also put a temporary credit of {$500.00} plus interest back to my XXXX credit card account. I reached back out to chase requesting the documentation and gave the Chase customer service supervisor all the information that XXXX XXXX requested. I assumed that everything was resolved until I received my XXXX XXXX statement in XXXX and the credit from XXXX XXXX was reversed. I called XXXX XXXX and was told that they never received the documentation showing proof that that the payment was received by XXXX XXXX. I called Chase on XX/XX/XXXX and spoke with XXXX. She told me that the documentation was sent to me, not XXXX XXXX by mail, but I never received anything. I was also told that the documentation could not be sent to XXXX XXXX. I requested for her to resend the hard copy documentation to me again, but as of XX/XX/XXXX I still have not received it. Currently there is a {$500.00} balance on my Chase credit card and {$500.00} balance on my XXXX department card. Trying to resolve this dispute on my own seems to be impossible to resolve. I need help from a third party at this point in time.