Product: Credit card or prepaid card

I am a Citibank , N.A . credit card holder of a Costco Anywhere XXXX. 
I have disputed a charge on my Citibank N.A. account for an XXXX purchase that I returned, which was eligible for full credit upon return. I have provided Citibank N.A. proof of the return authorization, tracking number, and proof of delivery of the return to the XXXX XXXX. Citibank failed to investigate the disputed charge or consider any evidence that I provided of the return, accepted an automated rebuttal from XXXX that failed to address the reason for the dispute, and denied the dispute with an automated message to my account. Citibank N.A. 's dispute investigation practices consist of an automated message to XXXX, acceptance of any automated rebuttal from XXXX, resulting in automated denials of disputes without any investigation whatsoever. This is in violation of their cardholder agreement in that they have failed to provide the consumer protection and recourse that their cardholder agreement promises their customers/cardholders. 
Relevant facts : When I disputed the problem charge with Citibank , N.A . I stated that the reason for the dispute was because the merchandise was validly returned. 
At no time did Citibank allow me to provide them any information about the purchase or return, or provide them with the proof of return. 
Citibank N.A. received a dispute rebuttal from XXXX which merely stated that the merchandise was delivered and does not address XXXX 's failure to process the return, nor reason given for the dispute. 
Citibank N.A. received this automated response from XXXX and immediately denied and closed my dispute. 
Citibank , N.A . 's cardholder agreement requires them to investigate a dispute. In this case, they did not. They received automated messages from XXXX that do not address the issue, did not review the information received, and proceeded to deny and close the dispute. 
Because the dispute was denied I am no longer able to address the dispute on the Citibank N.A. website or mobile application. 
This lack of ability or willingness of Citibank N.A. to process or investigate disputes is in violation of the Citibank N.A. Costco Anywhere XXXX cardholder agreement that I entered into and pay significant cardholder fees and interest toward. 
I would like CFPB to investigate Citibank N.A. 's dispute investigation practices, as it is clear that automation of the process results is automatic denials of almost every dispute processed, resulting in Citbank N.A. 's violation of their cardholder agreement in almost every case, and costing their customers/cardholders untold amounts of money in denied dispute charges. 

Account number of my Citibank N.A. Costco Anywhere XXXX card : XXXX. 
Name on Account : XXXX XXXX XXXX Charge that was disputed : XX/XX/22 XXXX charge in the amount of {$210.00} Reason identified in dispute for the dispute : merchandise was returned I have appealed the dispute denial by emailing all of my evidence of returned merchandise and eligibility for refund to : XXXX I have not received any communication from Citibank N.A. regarding this appeal. 
I have attempted to resolve the issue with XXXX, but have been unsuccessful, thus this dispute with Citibank N.A. is at this time my only recourse for disputing this charge.