Product: Credit card or prepaid card

We purchased a kitchen suite for {$4000.00} from XXXX. Like many Costco customers, we decided to buy it from Costco only because Costco promised that they offer a total of 4 year warranty including 1 year from manufacture, 1 year extended by Costco, and 2 year from Citi Card with which we pay for the purchase. One of this suite , dishwasher, had problems very shortly after we got it. We contacted Costco and had repair service twice and the whole dishwasher replaced once, all covered by XXXX warranty. We got very frustrated by the poor quality of this product but was still patient enough to keep using it for a while as we thought we had extended warranty to cover possible product problems. The problem unfortunately happened again some time last XXXX, the dishwasher stopped working completely. We did a lot of internet research trying to figure out what is wrong with it and tried to fix it. But all our effort failed even though we tried different ways. We than contacted Costco for return or repair that was declared by Costco as their extended warranty and 100 % satisfactory guarantee. Since we didn't contact them soon enough to catch the two year warranty by Costco because we were trying to fix it, we were told by Costco to contact Citi Card for extended warranty coverage. We had peace in mind as we had experience with extended  warranty services from XXXX XXXX multiple times on various products purchased from Costco. But to our great surprise, Citi Card even didn't bothered to contact us for details but simply denied our warranty request with only one sentence we had never heard about. It said in their letter, " As the product has a product defect, no coverage can be provided ''. We checked original warranty from XXXX and it clearly states that XXXX cover all the manufacture defects. Costco openly declare Citi Card extends original warranty for another two years. What don't know what Citi Card 's warranty extends and covers if product defect is not covered? This is obviously a violation of Federal Warranty law with a clear intention of taking advantages of consumer 's lack of protection resources. We then contacted Citi Card on XX/XX/2020 for their explanation of their unclear, ambiguous rules on coverage. I talked to a few representatives including a manager on a few calls for a few hours. But I was denied for coverage by all of them using this unclear statement. This is a very unprofessional, unethical and irresponsible business practice I have never had with all other merchants and extended warranty service provider for decades. They obviously use and manipulate fine prints to deny their warranty obligation at their will. At my second effort, I contacted Costco for help. I called a few times talked with a few people from different departments. To my surprise again. Costco refused to help me with this problem with Citi Card. Costco asked me to handle this difficult problem by myself with Citi Card. This is a very irresponsible business practice. It was Costco 's promise of 4 year warranty that mislead us in making the uninformed purchase decision for Costco product. Costco didn't inform us that the so called extended warranty actually won't cover manufacturer defects and what this extended warranty will cover in detailed and clear statements. We don't understand what this warranty by Citi Card really extends. It was a lye. It was not a warranty at all. Costco used that fancy statement of 4 year warranty to expand their business by tracking customers to make purchase at Costco but refuse to help their customer for their protection right. This is absolutely irresponsible, deceptive and unfair to consumers.