Product: Debt collection

Opened an account with XXXX XXXX while making a purchase in the store in order to receive a discount. Total amount came to {$150.00}. This total amount was paid via electronic issuance from my bank Chase JP Morgan XX/XX/XXXX. No other purchases were made on this account. Received a statement from XXXX showing a balance the next month. My thought was that the payment had not been received at the time of the statement generation. Received another statement the next month that included a late fee on the statement. I contacted XXXX and indicated that they made a mistake and that payment had been made to them. They requested proof of payment which I provided. There was an issue with the account number however, they assured me that they would be able to locate the payment by name/ dollar/ amount and trace information provided by the bank. They indicated that was probably the issue with the delay of application to my account. They removed the fees and a few months later it happened again ... I repeated the same thing and then they removed the fees and made a notation and submitted the account for research. I provided information again and also hosted a 3-way call with my bank. The bank confirmed the payment. I also provided a copy of my statement showing the money being taken out of my account. About 6 more months went by and I started getting collection calls. To each one I told the representative the same thing and provided the same information. Finally I wrote a letter to the CEO complaining and received a call back from customer service. They took the issue under advisement and promised they would resolve it. The collection calls continued and I tried desperately to get it resolved. By this time it had been over a year and XXXX XXXX XXXX was negatively impacting my credit as well another account that I had with XXXX XXXX for my XXXX XXXX account was directly negatively impacted. I received letters from XXXX XXXX  informing me that they were lowering my credit limit from the current {$1200.00} to {$800.00} then it went to {$600.00} and now to {$300.00}. This happened each time I paid down my balance. I went back and forth between my bank and XXXX XXXX both holding their positions. Chase maintaining that the payment was made and accepted by XXXX and XXXX maintaining that they never received my payment and it was still owed. In XX/XX/XXXX/ XX/XX/XXXX I started received collection calls from XXXX XXXX XXXX indicating that they had ownership of this account and I had a balance of {$430.00}. I explained everything to them and provided the same documentation. They said they would note the account and open an investigation. At the end of XX/XX/XXXX I received a letter from XXXX stating they received a debt validation request for the account with copies of the XXXX statements and indication that the debt is still owed. I filed a complaint and all XXXX stated was they did not receive the money and their biller code is not the one listed on the payment screen from Chase. At this point I am not sure who is at fault, XXXX or Chase however, what I am sure of is this money came out of my account and was sent and this has been paid and is not owed.