Product: Credit card or prepaid card

My dispute is with Citi Mastercard. 

In XX/XX/XXXX, I disputed two charges that I paid with my Citi Mastercard ( Citi ) for a purchase made at XXXX 's ( the merchant ) for one purchase ( that I paid for with two separate charges ) of countertops which included installation. 

The two charges were for {$700.00} and {$3000.00}. The dispute for the {$700.00} was settled in my favor, so my complaint is specific to the charge made on XX/XX/XXXX in the amount of {$3000.00}. 

When the merchant completed the installation, I was asked to and did sign a Certificate of Completion, which states the installation was completed but says nothing about the condition of the product or the quality of the installation, only that the installation was completed. 

Immediately I discovered several defects and issues not only with the countertop but also with the installation itself. I sent several emails to the merchant including the salesperson and the store manager and received no response. 

I filed a dispute with Citi who then allows the merchant somewhere around 90 days to respond. When the merchant finally responded to Citi as the 90 days were coming to an end they said I never notified them of my dissatisfaction with the product, which was not true, and cited that I signed the Certificate of Completion. 

Citi then sent me a notice that my dispute has been resolved in the merchant 's favor because " the merchant is not willing to issue credit to your account. '' I appealed their decision several times based on the fact that according to the Fair Credit Billing Act ( FCBA ) if there is a quality issue with the purchase and the charge is over {$50.00} and purchased in my home state, the credit card company is required to complete an investigation. In my case, Citi only and continuously, simply asked the merchant to give me a credit, which is not an investigation and is something I already did myself, I didn't need Citi to ask for a credit on my behalf, I needed them to investigate, which if they did a proper investigation, they would have determined the merchant was in breach of their contract and/or warranty and should have settled in my favor. 

I finally was able to speak to a Citi dispute department supervisor ( I believe on XX/XX/XXXX at approximately XXXX p.m. XXXX Time ) who, despite all their notices saying they can't help me because the merchant won't agree to issue me a credit, said they wouldn't help me because I signed the Certificate of Completion, which again my dispute with the merchant wasn't that they didn't install the counter, it was that they improperly installed a damaged counter. 

My claim against Citi is they have violated the Fair Credit Billing Act by not properly investigating my dispute. 

It should also be noted that one Citi dispute department representative XXXX XXXX XXXX said on XX/XX/XXXX, I could convert all my evidence against XXXX XXXXs to PDFs and submit them with a form to help resolve the claim in my favor ( their paperwork states that photos can't be submitted because " they are not compatible with our system '' ). I did that only to find out later that Citi won't accept any evidence from the customer, however, they accepted evidence from the merchant. 

I believe Citi Mastercard has not acted in good faith and chose not to properly investigate my claim for reasons unknown to me. 

Thank you for your assistance with this matter.